Luckily this hasn't happened to me (yet), but a friend of mine was scammed the same way in Athens, Greece. Except that he also got drugged since he only had one small drink but said he was feeling like he had drunk a lot more. I know he charged the "fee" but not sure if he ever disputed or what since he's not very good with that sort of thing.

Worst that has happened to me is in Manuel Antonio, Costa Rica where, upon getting off the bus, my girlfriend and I were intercepted by a guy who took us to a decent hotel/hostel and they suggested a tip for his services. Gave him $1 for the 5 minutes of his time and the hotel turned out to be pretty nice and right next to the park, so we were happy overall (and there was no shady business since my girlfriend knows Spanish and understood everything they were saying).