I have no idea if there is any legal precedent for requiring resell value on a prize, but these "rare drops" definitely do constitute prizes on a human level. And they by definition DO economic value (even if you can't resell them) because people pay money specifically for a chance to win them.
If value of something is how much the market is willing to pay for it: it had value before you bought it, and none after (you can’t resell!). Is there a difference from buying an “experience”?
