Answer:
20% hands down... Massage therapists work so hard! My sister is one, and it puts a lot of stress on her body and hands. Think about when you give a massage, how quickly do you get tired, and how much physical work it actually takes. They are using their own muscles over and over again, to make your body feel good. I have seen other comments that they get paid an hourly wage too... Yes, some do, but some don't, and it's very minimal.
I would say $20/hour is common courtesy. An hour massage can range from $60-$150+ depending on where your massage is given.. (spa more expensive and they most likely get paid higher hourly) If you are receiving a massage from a spa, well then adjust tip according to the way you feel. If its $150/an hour massage, I would at least give $20 minimum, but if it was all that and more, 20%.. $30 tip is well deserved.
To work so hard, physically on other people, even if an hour massage only cost $60 initially, you don't know what they make hourly, and 20% of 60 is $12 tip. $12 after I just put my hard work into make you feel relaxed for an hour!?!.. Is like handing them a few quarters and saying thanks.
But for someone massaging me for a whole hour, deserves at least $20. Even if the massage cost $60 dollars, they are not receiving that $60 dollars unless they are doing massages in their own home, then I would say give 20%.... because it's mainly all profit for them. Adjust tip based on their performance, but speak up!!! If they are not hitting the area you want them too, or if something hurts, tell them, and they will adjust it to your liking. Before deciding to decrease their tip, I would at least make sure that you have spoken up, and if they still could not tailor to your needs, adjust appropriately.