I only know one guy that sells what I do and does free shipping... But I think he is insane, because he sells stuff so cheap to begin with, I don't even know why he bothers being in business. He must be incredibly bored or something.
But yes, I think a way around the return issue is using a restocking fee. Which I've actually thought about doing anyway, because we simply don't have defects... and if something is askew on our side, normally I can just send a missing part, which I do for free. But anything else would be a customer simply 'trying' something out... which turns it into a used item, which I don't believe I should have to pay for. But luckily that rarely happens.