You're talking about the fs places. Tips at semi-legits can range quite a bit and many times, it's not much at all, like $20 (and don't forget they have to give a portion back to the owner). A couple of MPAs told me sometimes customers go for a 2hr massage and just tip $30. In one case, the customer even asks for MSOG. The MPA does it but says the guy cums in like 10 seconds so it's not that bad...but yeah, she's not too happy about the $30 tip. And he's a regular customer too. So yeah, they have to take the good with the bad...
Also, at these slower places, it's not unheard of to get 1 or 2 customers per day (and sometimes none at all). And if there's no customers, they still have to be there all day (plus cover their travel expenses, etc.)...