Remember the legend of Atari dumping tons of unsold games into a desert landfill in 1983? And then the discovery and excavation of that landfill earlier this year? Well now the city of Alamogordo (where the landfill is located) has begun selling the buried games on eBay. And for some reason the E.T. cartridges, a game deemed so awful and worthless Atari DUMPED TRUCKLOADS OF THEM IN A LANDFILL, are now going for over $600. For reference, that is entirely too much to pay for a piece of shit. Unless it's a dragon or unicorn turd, in which case, okay, those are rare potion ingredients and I'll give you $550.
Thanks to William, lean and Stephanie A, who agree your best bet for procuring potion ingredients is the black market, but you have to be careful because a lot of witches will cut their products with less magical ones.