While normally this would be on the verge of being a scam under any other situation, but because there is actual documented proof that the air is actually a drop, it could be considered unique since it can only be aquired this way.
However, this is a scam since they are using a chest to trap air. I bet that thing isn't air tight at all, given the big ass lock, and the decorative edges. So by the time it reaches the customer, there is no way to prove the air is still the same air dropped by said skeleton.