I don't know the price of Project Justice right now, but the game is definitely worth picking up. Basically take the same game, up the graphics, and add more characters for each school. Wild Daigo and Zaki are two characters I really like that are only on Project Justice, but pretty much every other character on the original Rival Schools is on there as well(except the custom characters I think.)
It's been an extremely long time since I've played the game because I didn't own it, my friend did. I only own the PSX Rival Schools.
I liked. It gets old fairly quickly but it's really fun playing multiplayer. Good came considering it's a one button fighter.