Ok, businesses go all card-only, saving money on operations and security, on the assumption that everyone either has a card, or can buy a pre-paid one at their local post office. The latter - the cash for card exchange - is a cash flow in one direction, from people to the post. But how does cash flow back to the people again?

Obviously, if businesses refuse to accept cash to save themselves some hassle, they'll also refuse to pay salaries in cash, to save themselves further hassle.

The incentives are there, and it's clear to me that if you simulate it forward a couple cycles, cash will be all but gone - with the remaining few businesses and people using physical money automatically considered suspicious.