What I am trying to say is most of the time there is no such thing as final sale. E.g. a hobby store near me says final sale on electronic parts. As I am aware this is not allowed, they actually have to prove the customer broke the part to refuse the return. This is pretty hard to do.

They also can't charge restocking fees or refuse the return if you've destroyed the packaging. Losing the receipt possibly, but they need to be tracking sales as well and I think you would win that.