That's right. But the retro games are old, so they shouldn't sell for that much. Maybe $15-20 is a more reasonable limit to put to yourself. Also I'm not that kind of guy. I just don't have the money.
Yeah it's mainly an offer vs demand issue. Most true retro gamers will want to play the old school way, with the original game and console. Some don't even want the NES/SNES clones like the Retron or FC Twin. However, since those games are discontinued in their cartridge form, they get quite pricey if they are in high demand like Final Fantasy III or if they were originally produced in very small quantities (Hagane, for example, was a Blockbuster exclusive for rental, so very few copies were made, so now it sells for $400).