A Ferengi would be smarter: the customer gets compensated with a non-exchangeable coupon that provides him with another drink (of lesser value), plus an extra drink only available from this establishment the next day.
Really, actually giving money back basically never works ITRW.
Timo Saloniemi
In the case of a drink at a bar or some retail item, yes, but in the case of a business agreement where he did not deliver on contract, attempting to give some kind of credit could be construed as insulting. Better to maintain a good business connection.
The Rules of Acquisition are just greedy aphorisms. Peace is good for business, war is good for business! Never sleep with the boss's wife, always sleep with the boss! 20 variations of 'Women suck'. Short pithy sayings that validate the Ferengi impulse to patriarchal, deceptive, short term high risk ventues. In the show, Quark's biggest successful profits that we see came as a result of fostering loyalty (Who Mourns for Morn). Sure, his biggest losses of profit have been sentimental and moral in nature (Rules of Acquisition, Business As Usual). But Quark holds the knowledge most of the series even if he doesn't want to admit it, the Rules as he memorized them don't make you money off Ferenginar. You can't make money off Ferenginar without fostering loyalty.
IMO the Ferengi are usually best in non-Ferengi centric episodes. When Ferengi other than the regulars get involved the story tends to immediately get super-cartoony.