Profit disappears when Competition is Perfect, but Competition is usually not Perfect, so Profit is usually not Zero.
Profit and Competition are inversely related, while Profit and Monopoly are directly related. A Perfect Monopoly would enjoy Infinite Profit, right?
I found, that these theses are wrong, because they base on on the assumption, that profit raise from the circulation of commodities. Profit is not explainable as a difference of prices. But where else did the profit come from? What is profit at all?