We'd never need to buy paper if we pulped and recycled junk mail and receipts. We'd never need to buy dirt if we composted all our food waste. We'd never need to buy anything made of plastic or aluminum if we melted and molded them ourselves. We'd need to buy much less wood if we collected all the discarded pallets
Unfortunately there are economies of scale involved in such labour, and it's really hard to reconcile with e.g. wage slavery under crapitalism.
Sunbeam City is a Libertarian Socialist solarpunk instance. It is ran democratically by a cooperative of like-minded individuals.