If 'no one has any income', then prices become 0.

There will always be a relative few people with income. The business owners, property owners, asset holders, landlords, and so on. Those are the people who prices are set for, and who will participate in the economy. The rest of us? A lot of us are already essentially economically irrelevant in the grand scheme of things, and more and more are becoming so every day, even as they nominally get richer.