I'm still interested to see what logic Ic's there using.
here is a pic of a bootleg i found of the fds game, I assume some one in the 80's placed one of these in with an adapter in your cartridge.
edit,
Id value it less the $30, but no higher then $50. Supply and demand. As new repro of this fds game do exist. For as high as $50. With no donor parts. That also work on any version of the nes.