This does not seem obvious to me. Humans have a strong competitive drive; I do not see why profit should necessarily drop out of a post-Friendly Singularity society, even if what we buy with our Shiny Future Moniez are perhaps status goods. Moreover, considerations of acausal trade to increase the probability of AI being Friendly seem to suggest that its inventors should get some sort of reward. This said, it is of course not clear that such a profit would be taken out in US dollars.