He will only give me $50 for my bran new dsi!?!?!?

i went to trade in my dsi bran new, and he said he will only give me $50! he said it was because it was from china and didnt play dsi games! there is know such thing as a dsi game, it plays any games normally and looks like any other australian dsi, i know my grandpa got it from though but all australian games work on it.... so is there any way i can get him to give me more for it?