You make some good points. Foremost is underwear/knicks and toothbrushes (aka intimate objects). Those are a no-no. So there are some things that you should not be able to return for a refund (like medication).

But there is that new category of things with too little actual value to be worth processing like pillows and compressed mattresses (once you allow them to expand, you cannot compress them at home.)

But a lot if the problem in returnable objects where a return is not cost effective has to do with shipping costs. Shipping it back + processing costs cuts into profits and the resale value does not compensate adequately. Fortunately for them, the "returns" ratio don't negate overall profits.

That said, when it makes sense to me, I will buy from Amazon's warehouse deals --there are some good deals to be had.