I think there are levels of post scarcity and 500 years will not make money obsolete.
I can even grant you a millennium. Imagine fully automated world. The solar system is colonized. There are no human/posthuman being that lack any basic need – food, shelter information, freedom… At that point the total population of the solar system in physical form (altered, augmented or cybernetic) may be 10 times bigger than the current population of the planet and the digital population could be unimaginable number. Maybe we will be in the middle of constructing Dyson Swarm which will give us more living space than all habitable planets in the galaxy combined. And still there may be scarcity, because we are humans… and we are never happy with what we have. If we want to create synthetic black hole we will need more energy than the solar system could offer us. Or if we decide to colonize the stars we will build generation ships as big as cities. Such projects will create scarcity for other projects…