maybe Quark has to pay an energy bill even for using the drinks replicator.
I think this is the main part. Things cost money on DS9 because the energy used to run the replicators is a finite resource, given that they are in such a remote location.
I am Worf, son of Mogh, House of Martok, son of Sergei, House of Rozhenko, Bane to the Duras Family, slayer of Gowron. I have made some chamomile tea. Do you take sugar?