Gamecube- The cheapest is probably Baten Kaitos and its sequel Eternal Wings. Final Fantasy Crystal Chronicles is above average.
GBA- Advance Wars 1+2, FF Tactics Advance, FF4 Advance
PS2- Ton of RPG's for a generally cheap system. Final Fantasy 10, 11, and 12. Disgaea 1+2, DQ8, Persona 4, Kingdom Hearts, Xenosaga I, Tales of the Abyss.
3DS- SMT IV, Etrian Odyssey IV, Code of Princess( if you go to the $20-35 range, you can also pick up Fire Emblem Awakening and Bravely Default)