See, I'm just not 'buying' that. There will always be things that people want, whether it's an iphone or the latest transporter installed in your living room. And unless resources are unlimited, there was to be a value put on the exchange of them. Likewise, someone still needs to do the grunt work of civilization, and those people surely aren't doing it to fulfill their hunger for knowledge.
Humans are stil gready, they're just greedy for knowledge, creation, science. In 24th century, they don't care about having the latest Iphone.
I also think if they make humans too perfect, it makes the show boring. How many of us rolled our eyes when Picard made that statement about money? To me it was what was wrong with that episode, they tried to make the 24th century humans too far removed from us, which made them unrelatable and unrealistic.
Yeah there would be a value placed on them. You'd only be able to get the transporter through some sort of credit system from the state. An iPhone would be a custome made device, and you'd pay however the person that made it wanted you to pay. That's not part of offical economy that Picard would talk about because it's insignificant compared to the state economy. However, I bet that the person would make you pay with whatever credit system the state deals in because gold wouldn't be too useful.
I myself buy it because there are plenty of people who don't care too much about gimmicks. In the 24th century, there is a lot more of them. Considering the nature of the collectivistic society they have, it's not too hard to believe nor unrealistic.