> when 'all you have to do is to try to define what "the same thing" actually means', you, other people, and aliens' efforts might lead to different definitions.

Well, yeah, they might. But I'm assuming the aliens understand physics, in which case only one definition makes sense. You can snooker the irrational and the ignorant into paying for anything regardless of what species they are.

On which note, I have this nifty bridge you might be interested in? It's available at a great price. And it is the original!