Updated on 06.13.07

Comparison Shopping: Comparing The Internet To What’s On Your Store Shelf

Trent Hamm

For about the last year, my wife and I have purchased several household items in bulk from Amazon. Not only is the shipping free, but we don’t pay sales tax and we rack up lots of bonus points on our Amazon card by doing this. Our philosophy is that if Amazon has the same or even a slightly higher price than our local shopping outlets, we buy the bulk item from Amazon. Here’s the process we use to ensure that we’re getting a good deal.

First, we do weekly checks of the level of our supplies. We check the amount of diapers, baby wipes, laundry detergent, shampoo, soap, cleaning agents, toilet paper, and so on. This is part of our normal routine for preparing our weekly shopping list – if we notice an item is getting low, we add it to the list.

Next, we check for prices on Amazon for some of the bulk items before we go shopping. We just look up the items we need on Amazon and note their prices and their sizes. Here are four examples from a recent shopping trip:

Lever 2000 Energize (our preferred soap) @ $17.41 for 24 bars, or $0.73 a bar
Pampers Cruisers (stage 4) @ 39.79 for 140 diapers, or $0.28 a diaper
Pampers Wipes @ 23.54 for 770 wipes, or $3.06 per 100 wipes
Colgate Total @ 22.41 for 6 7.8 oz. tubes, or $0.48 per ounce

Notice how we’ve broken them down into cost per unit, so we can easily make comparisons at the store. Also, to save time, we keep most of our regular purchase items bookmarked so we can quickly run through them and retrieve prices – they actually vary quite a bit, and there are times when Amazon is the better deal and our store is the better deal.

What about other brands? We generally follow Consumer Reports’ recommendations for item quality and because of that we rarely have significant problems with items not working like we hoped. Even though the prices are often higher per unit, it’s worth the additional price on such items if you’re not finding them frustrating or of low quality. That doesn’t mean we completely abandon sale items; we generally find about four or five brands of each item acceptable and will buy these if there is a significant discount.

Once we have our Amazon prices in hand, we head to the store. We generally buy most of our bulk items at a warehouse store, so we buy our bulk items there first. We usually do any needed cost-per-unit math on our cell phones and then buy the option that has the lowest cost per unit – to a degree. If the prices are very close, we usually go with Amazon because (1) they deliver to the doorstep, (2) we earn more points through them, and (3) sales tax (in some cases).

What about coupons? If we happen to have a coupon for an item, we bring it along and use it in our calculations at the store. If the item is still cheaper at Amazon, we don’t use the coupon – in fact, I’ve actually handed coupons to other shoppers in this situation that were appearing to be about to buy the item.

Doesn’t this take a lot of time? Not really. Usually, both of us go shopping (we make an activity out of it with our child, trying to instill a healthy and rational way to shop, and we usually interrupt it in the middle with a trip to a park and a picnic lunch) and one of us is looking for items while the other is calculating prices. It doesn’t really add any significant time to the equation, especially if you would actually spend any time at all comparing two items and trying to decide which one is the better deal. That’s what we do – we just have a plan when we walk in the door.

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  1. Mark says:


    Something bothers me about what you said about free shipping. Have you calculated how much gas you used up during these trips to your store only to end up not buying them and driving back home to order them online. I can understand if the store was a 5 minute walk but if it was a 30 mile round trip, you just lost 5 dollars. Does the savings make up for the loss of gas expenses?

  2. It can, if he’s not buying one item per trip. It’s easy to see how this is cost effective if replenishing multiple items.

    Personally, I love coupons. My friends make fun of a young guy using coupons, because it’s “too much of an old person’s thing”. I make fun of them for not saving up to 50% of their grocery bills just because they won’t take 15 minutes a week to clip coupons from the sunday newspapers.

  3. John says:

    I’ve been trying the comparison shop route but can’t use amazon as amazon.com doesn’t ship to Canada and amazon.ca doesn’t have nearly the selection it’s american counterpart does. Nevertheless, I compared prices for many items at two competing supermarkets and found that one was cheaper for about 75% of the items we were getting.

    However, the pricing was done at non-shopping times, adding commuting costs in the mix. As well, I found it took about an hour at each store to find and price everything on my list and do the calculations of unit cost. This may seem like too much overhead to be truly cost-effective, but if it is done for a month or so to establish a large database of items you commonly get, in the long run you will save both time and money as this “extra cost” goes away.

  4. Cindy says:

    I don’t know what the tax laws are in Iowa, but in many states, you still are obliged to report these items to the state and pay a use tax on them.


    I read a story recently about a woman who had bought a lot of furniture out of state, and the following year received noticed from her home state that taxes and penalties were due. The furniture store had been audited.

    Taxes are not due if you pay sales tax in the state in which the item was purchased.

    But the laws vary from state to state, I just don’t want to see your readers get into trouble.

    Gosh, I’m so sorry to point this out, because I love your blog!

  5. Bill says:

    You really need to pick up a copy of the “Tightwad Gazette” book and review her concept of the “price book”

    You are groping towards that concept in this post.

  6. Lynn says:

    “That’s what we do – we just have a plan when we walk in the door.”

    Thats the key in a nutshell. My husband and I scour the ads weekly and save a fortune, but to save that usually means a 16 mile drive to the store with best prices. On average we save $40-60 however last trip netted $100 savings! Never could have done that without a plan.

  7. Kevin says:

    You spend over 70 cents for a bar of soap and you call yourself frugal?

  8. Adam says:

    Yea, you are supposed to pay the tax for the Amazon purchases. I believe it’s called a use tax.

  9. Ed says:

    I have to echo Mark’s comment, about not buying an item. If the price is the same or very close, I would buy it there just because you are already there (kinda makes the delivery to the door moot). I probably would make a note for the next time we needed the same item and get it via Amazon.
    I just feel it wouldn’t be worth your time to not buy something when the prices are similar and you are already there.

  10. Ed says:

    I forgot to mention, how hard is it to make your own bar soap?
    Maybe just a variation on the homemade laundry detergent?

  11. The Landlord says:

    Just to chime in an affermation, not paying taxes on your purchases is illegal. Since sales tax is instituted at a state level, and taxes are due to the state where the goods where purchaser is (not the state that the company is in), companies like Amazon are only required to charge taxes if you are located in a state where they have a physical presence.

    If you are located out of that state, you are required by laws to report the goods you purchased on your state tax return, and pay the appropriate taxes.

    Admittedly, no one actually does this. In general almost everyone just ignores that part and enjoys their goods tax-free. But if I were you, I’d be careful about publishing that in a public forum.

  12. jamie says:

    There is a terrific webservice called Frucall. Setup a free account online, then, from your cell phone while in the store, call up and enter the upc/bar code, and Frucall will tell you the cheapest prices online, including shipping costs. I recommend everyone check it out!

  13. Honest Abe says:

    If your state has a sales and use tax, you report it when you file your income taxes. Leaving it out is cheating on your taxes, period. If you don’t like it, it doesn’t change it.

    As for the actual info, I have checked Amazon’s pricing. It is nothing special. I mean, it beats the local grocer, but it doesn’t beat Wal-Mart. If you order items from Amazon that you have or could get coupons for, you are losing money. If there is something you buy that you don’t find coupons for then Amazon may be a cool way to stock up and save time. But, if I have a coupon in hand, I’m hitting the Wal-Mart Supercenter and using my coupon. That will beat Amazon every time IMO.

  14. GHoosdum says:


    I’m curious as to why you joined a warehouse club if you tend to purchase your bulk items on Amazon? The main reasons I shop at a warehouse club are to purchase the types of items you talked about in this post, and my produce, which you purchase at the local farmer’s market…

    What does that leave you purchasing at Sam’s?

  15. GHoosdum says:

    On second read, perhaps we have a different definition of “bulk items” – my bulk items tend to be things like mega packs of soap and diapers (if I had children), yours must be different since you refer to usually buying your bulk items at the warehouse club, and usually buying your soap and diapers on amazon…

  16. MB says:

    Just curious and new to your blog — why are you buying name brand (pampers) diapers and wipes? I save a ton of money on Costco diapers and wipes, and if I run out of those a little early, I’ll buy CVS generic. At costco, I’ll get 200 diapers for $35 (and they frequently have a costco coupon for an additional $2 or $3 dollars off.)

    My buying of soap is also a little different — I buy luxury spa soaps, but only at a Marshall’s or TJ Maxx. Usually $3 or $4 a bar. The trick is is that I buy one of these soaps when I feel like a little splurge and feel like going shopping. Beats buying myself a $50 pair of shoes or a $20 sweater, and it feels very nice and decadent every morning in the shower!

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