The very same guy bought a Steam trading card from me at 50 euros.
And my god, did I feel like an idiot after that. He would've paid thousands just for the sake of being the first one to get his hands on a virtual badge on his virtual Steam account. And I sold one of the pieces to him for just fifty euros...
Sigh. I doubt I'll ever again be the first person to get a Foil card of anything ever again, but if I do, lesson learned: start high. For people who have more money than common sense, the price is just a number.