How much are these three original Japanese GBC tapes worth?

I think it is expensive. I don't know if there are any boxes, manuals and the like. How long did the battery last? The key point is that a burn-in card is only over 100 now. Now there are fewer children playing GB, either NDS or PSP, and it is basically impossible to sell.

It is better to keep a souvenir than to sell it, unless you really need this 100 yuan urgently.