I'm confused, are you playing NES games on the Famicom or Famicom games on the NES? Adapters to play Famicom games on the NES are somewhat common, I've never seen any worth $50 unless the price jumped recently. I've found these to be worth around $15, and I thought people looking for Gyromite carts just wanted to get an adapter for under $5. I used to include adapters for free with multicarts when I sold off spares.
I found several adapters for under $5 each, usually with some Famicom game with it. Usually the game would be a multicart. What was hard was finding an actual Honey Bee adapter but I managed to get one too.
Famicon games on the Nes ...
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