I've been stung by this before, but my fault for not negotiating the tip beforehand. Took a Jupiter guy back to my hotel for short time and when it was all finished (which tbh was average at best), I went to give him 3000 but he then told me his rate is 5000. As I'm relatively small and the guy was bigger than me, I didn't want to escalate the situation or cause a scene so we settled at 4000. From then on, I now check with guys (that are new to me) their tip expectations to avoid surprises like that.