Some guy wants to buy a Megadrive converter cart from me ...

I have a few about the place, including:

A loose "Mega Key" (with 4 dips switches on the back) and a table on the front showing positions to set for various regions.

A "Mega Key 2" - boxed (no dip switches, just a plain cart with a sticker saying "Mega Key 2" on it.

They both work ... what should I be asking for these? I don't want to fleece the guy ... but neither do I want to pass one of these on for a pittance if it's worth a bit.

Vroomfunkel