One thing about Quark's bar is if he served real food where was his kitchen?
I tend to believe that people pay for food at Quark's because it's his recipes, even though they're replicated. It does seem like he's got a sweet scam going there. His landlords don't ask for anything from him for the energy requirements of his replicator, so his production cost is near zero. And since we know he pays his employees next to nothing, most of his earnings turn into profit. I remember Sisko once blackmailed Quark into something by threatening to charge him back-rent for his bar space and power consumption. As the Grand Nagus once said, "You've done very well for yourself, Quark. Who knows, maybe one day I'll come back to your bar and buy it from you."