It's less so the taverns own money and more so that the food, wine, bar (or future visits) subsidize the beer, ie the food is taxed so that the beer is free.

Same with credit card rewards, they're not paid for by the bar, they're paid for by volume at the bar, debit/cash transactions, and the savings on cash controls, and the people that can't payoff their credit card bill.

An economy is not a zero sum game.