Federation credits? Federation credits are no good out here. I need something more real.

This is just a world building issue that comes with hundreds of writers over the decades. Who knows how money works. Someone will say something, then ten years later, another writer wont get the note and write something that conflicts.

That's the greatest accomplishment of the Federation, tricking the Ferengi! Internally money isn't used anymore, but to trade with the Ferengi they use these Non Federation Tokens, which have no real value.