I hate the idea that it’s mandatory to accept returns that are not duff. Nice if you want to offer that facility but to impose that is wrong.
Not accepting returns would be the death of Internet shopping IMHO. Why would you buy, say, a pair of shoes online if you couldn’t send them back if they didn’t fit? (Also, if you can’t send stuff back it opens the door to shysters who will sell any old shit and not care). The whole point is that it’s to empower you to buy things unseen.
As for costs to the business, well, they’ve not got the overhead of running a branch day-in, day-out when there might not be a single customer. The hit they take on returns surely can’t be higher than employing a shopful of staff in an empty shop?