I think the argument is slightly more convoluted, so it survives your criticisms.
Let's imagine a society where there is one thing which everybody wants (say, food) which is controlled by one big corporation (say, monsanto) with few owners. There very well can be a parallel economy between people, but for the economy to function the few owners of this big corporation must want stuff from random people just as much as people want food. The moment this small number of people control something which far more people want than they want anything you will have an infinite sink; that is, each year a certain supply of everybody's wealth will be "eaten up" by the corporation without anything flowing back in return. With technology you can conceivably have a few of these (say, Larry Page or Mark Zuckerberg can't possibly want enough things to not be effectively huge money sinks in the short term), and if you have enough of these you will have a crippled economy.
> Let's imagine a society where there is one thing which everybody wants (say, food) which is controlled by one big corporation (say, monsanto) with few owners.
Why imagine that and not unicorns that fart gold bricks?
Yes, unicorns don't exist, but your scenario doesn't exist without significant govt intervention, intervention that doesn't have to occur.
Let's imagine a society where there is one thing which everybody wants (say, food) which is controlled by one big corporation (say, monsanto) with few owners. There very well can be a parallel economy between people, but for the economy to function the few owners of this big corporation must want stuff from random people just as much as people want food. The moment this small number of people control something which far more people want than they want anything you will have an infinite sink; that is, each year a certain supply of everybody's wealth will be "eaten up" by the corporation without anything flowing back in return. With technology you can conceivably have a few of these (say, Larry Page or Mark Zuckerberg can't possibly want enough things to not be effectively huge money sinks in the short term), and if you have enough of these you will have a crippled economy.