Communism still has currency.

I don't know why this is a popular misconception. You may have ration points or communism bucks instead of dollars, but you still need a hard currency to allow interpersonal trade. You may have resources that aren't obtainable through currency (housing), but you need currency because you need to settle preference/availability/tradeoffs. You probably also even still have some taxes for consumption.

The price of all goods is not equivalent on a fundamental labor level and the preference for goods is not flat.