I mean, Piketty posits that a period of low/no growth tends to also correspond to low/no inflation. The real material cost of things is going to shift as we divorce ourselves from the global economy. If you can't get cheap imports from China, Marx will tell you what that'll do to the price of a coat.

But we're still a post-industrial society. If nothing else, a shrinking population will produce a vast surplus of hand-me-downs and other used goods. Same thing with housing.

What's ultimately going to change is the relative cost of things. Water will be scarce but consumer goods will be over-abundant.