As I said, my personal opinion - I don't expect to convert anyone...
If you were instead to purchase 1 bag at a time, try it out and if you liked it, keep it, that'd be a totally different concept to me. But planning from the start to return 2/3 of your purchase gets annoying.
Keep in mind, I'm refering to the general practice. It is possible to do it without being a problem, however most customers do not return items in like new condition and in many packaging cases, it's actually impossible to try it on without damaging the packaging.
Most of the time they lack tags, packaging and such - the retail stores do not have replacement packaging from the companies so they often have to sell it as a demo unit.
From the company perspective:
We pay for someone to get said product listed and whatever other operating costs so you see the product.
We paid a cost per click (anywhere from $.20 to $2.50 each)if you used a search engine ad to find the product.
We get the sale, we lose 3-7% of the sale price on credit card processing.
We pay someone to print out the order, pack it and ship it (could be just a few bucks)
You receive it - but you already had a bag you like so you return it - your cost is just return shipping.
We have to pay someone to handle the RMA process.
We have to pay someone to accept the package and process the returned product.
We have to pay someone to process the transaction return.
Depending on the processing system, often we lose a % on the reversal processing.
We then have to pay the bookkeepers / accountants to handle the transaction reversal and any losses associated with the return.
We are then left with a product with opened packaging, torn cardboard tags and often meaning we have to return it to the vendor for exchange, sell it at a discount, or put it out as a display product. In some cases the opening the big plastic bag that the sleeping bag is sealed is enough to cause it to be value lost.
All told, it's one of those hidden expenses the consumer never thinks about, but it's the bane of small business and cottage industry owners - or it is if they are paying attention to trying to stay in business. For a big retailer, they often work out an assumed cost of doing business for returns, for smaller businesses, the practice can lead to significant price increases to offset the practice.
All of the above said, I want my customers to be happy with their purchase and will do what it takes to make that so and will gladly pay for the return if that's what it takes. However, the bottom line is that flippant returns raise prices or decrease retailer viability - often hitting smaller retailers the hardest.