It's sound reasoning up to a point. It would be far more efficient if everyone gave their RAM to a central collective and used it online. That way the RAM would be in use even when you aren't using it personally. Everyone would have an effectively infinite amount and it would be cheaper because you only pay for the time that you are using it.
I'm reality, of course, Sam would be in charge of all the RAM and would keep screwing us harder and harder until we started squeaking like a rat in an undersized corset. That's what separates the theory from reality.