In the case of Prikura, it's the exclusivity that's driving the price. There are fewer and fewer games on the Saturn these days that are still the only place to enjoy them. Taito Legends and Xbox Live Arcade took a few exclusives out of the Saturn's library.EAR was at $25 three years ago? I'd like to know where you bought it from. That game was consistently above $100 ten years ago.
Prikura, on the other hand? InfiniteNine and I were just laughing at that price the other day. No, it is not worth $550, it is not worth $50 IMHO either.
The pixel art's nice but the game's very ok and it's not one of the better shmups? Pick up a Taito shooter like Layer Section with that money instead, if you can't swing a Raizing game.
E: Preferable to own Galactic Attack over Layer Section though no?