Personally, I just assume that the "there's no money" stuff is a load of crap spouted off by people like Picard who want to come across as morally superior. We see plenty of times in Trek evidence of money, commerce, private property, etc. From Kirk talking about how much Starfleet has invested in Spock and Spock starting to spout off a dollar amount in reply, to Scotty buying a boat, to people buying and selling tribbles, to Beverly buying a bolt of fabric, and on and on. Money clearly does exist in the Trek universe.