There is a massage charge, $60 for 1 hr usually.
When someone is asking about a "tip", are you interested in the amount you offer the attendant on top of the room fee for special attention, or do you mean on top of that?
If you want to leave happy, most attendants will require an additional fee, I find an amount I am comfortable with to be usually about the same as the room rate. In general, you can pay a little less or more, and may find the attendant willing to work harder or pay more special attention based on compensation. Some may ask if you want a certain area massaged, and if you respond yes, they may ask how much you are willing to "tip" or "spend" which I can see would lead to this confusion in terminology.
In my opinion, a "tip" would be something you give on top of the negotiated extra fee if they did a very special job above what you expected for the negotiated amount. And, should you be interested in repeating and getting the same, or even better service, I highly encourage this practice.