Various thoughts responding to posts here. Not in any particular order.
I've been a moderator of a Kindle forum for over four years. And without a doubt, there are people who buy books, read them OR save them offline and then return the book. People have posted here to that effect. Not so much, anymore, as it's very clear that our culture here on KB is that that's NOT an appropriate behavior. So those people rarely post here. But they exist. And if a few post here that they do, that's just the tip of the iceberg. I still don't think it's most readers, but they're out there.
Based on the same anecdotal evidence, apparently, it's really, really easy to buy a book by accident if you read samples. I don't, and rarely buy a book by accident. I have bought a book on occasion for purposes of testing something here on KB and then returned the book. I apologize to the authors of those books. Though I don't think James Patterson or Stephen King were much bothered by it when I did it with their books.
Probably an argument could be made that the seven day return window is a bit overly generous, but I think two days is not enough. Many companies have generous return policies and it works well for them. Radio Shack and Nordstrom come to mind. Their customers respond by shopping there first. No doubt that is Amazon's goal.

I would consider it a cost of doing business and do what companies with those kinds of return policies do; include that cost in your pricing policies, as much as possible. It's going to be a fact of life as long as Amazon has that policy. Obviously that's easier to do if you have a lot of sales and just a few returns. But if you have a significant number of returns, perhaps you need to consider that there are more issues than just customers taking advantage of the return policy. Just sayin'.
Note that Amazon will refund for books that have serious formatting issues even after the seven days, in recognition that many books do not get read right away.
As an aside, I have bought an app by accident, and apps are generally not returnable. Though if you throw yourself on the mercy of Amazon's CS, you can get your money back for a rare occasion. (Same with Apple--I was stupid once and downloaded the wrong version of the app; they refunded my money.)
Anywho, my .02 worth. Or maybe less.
Betsy