I hear people talking about "having money for dealing with cultures that still use money". Isn't that almost Prime Directive territory? I'm Joe Ferengi eking out my meager capitalistic living in my scarcity based economy. Now here comes Ensign Fed. He can have my entire store if he wants because he has limitless "buying" power. His money isn't "real", it's just an interface between his enlightened post-scarcity culture and my Yankee trader one. Ensign Fed can totally and singlehandedly destabilize an entire non-Federation culture and economy.Methods of compensation to other species outside of the Federation does not mean they possess any internal financial systems of their own.
Unless the Federation put some kind of brake on Ensign Fed's buying power. But that means that our poor Ensign now has SCARCITY. His "interface" now has an actual VALUE. It becomes, dare I say it, money. He might want to get more of it somehow. Sure he can replicate anything he wants, so there's no point in a shipmate giving him more "money" for a rare 2237 Boston Dodgers Zero Gee Checkers Team trading card. But maybe Ensign Other Guy might give Ensign Fed some more "money" for an extra recreation period? Or Ensign Attractive Classmate's phone number equivalent? Ohhh, that's starting to sound like an economy.
But that's all unnecessary because back in the 23rd century the Federation had money. Even when the Great Bird was making it all happen.