Even with full automation, you still have the problem of coordinating the economy as a whole, in a way that can't be gamed or controlled by any one person. And

Even with full automation, you still have the problem of coordinating the economy as a whole, in a way that can't be gamed or controlled by any one person. And you'll need a way to rationally allocate resources that takes into account new innovation, when people disagree. For both these reasons, you'll still want market pricing. Even if all basic consumer goods become non-scarce (and therefore free), there will always be some upper bound at which goods are still scarce. Another way to say this is that prices will get very, very low, but not zero. If energy costs zero, then anyone who wants can launch a mission to Alpha Centauri. But if energy costs the average person $0.10/year, it's practically free, while still being rationally allocated among really big users. There will always be things that are so ambitious they have a price. Star Trek's moneyless economy is fundamentally contradictory: in a truly scarcity-free world, anybody who wanted could own their own Enterprise-class starship. (How does an unemployable human come up with even $0.10/year for their energy, etc? They, or their government, or a charity, just need to own a little bit of the robotic factories paying dividends.)