I suppose that Greeks could begin selling their production for export at some discount to foreigners for BTC and then use that BTC for local trade. The people

I suppose that Greeks could begin selling their production for export at some discount to foreigners for BTC and then use that BTC for local trade. The people outside cities who have land and use that land to create food (plants and animals) could eventually bring enough BTC into the hands of Greeks to make the economy work in a somewhat normal fashion.