Oh I know your pain. Same thing happened to me with a Civ 5 foil and with a bunch of Mystery cards. But this was from a Witcher 2 drop when there were still only like 7 on the market. The earlier you can get a card on the market the more you will make.
One of my cards is a Go Home Dinosaurs foil, Bruno Stegosaurus. There's never been many of them, but nobody wants to make a dinosaurs foil set... Another one is an anodyne Fisheman foil. Again, hardly anyone buys them, and everyone's been slashing prices since the beginning of the month...
I was the first one to have a McPixelette foil, and put it on the market for a decent price (like, 3$). I eventually got about 60 cents for it.
Man, I really miss the beta, where people were actually paying good money for foils.