If you tip around $40-50, these girls see you as good customers,nice guys, talk to co workers, remember you well and will treat you much better than others. They also know about some regulars who tip them only $20 all the time. They are not very fond of them and try to stay away from those guys as much as they can if possible. Even if they do have to serve them, they will give them a mediocre service. Some of these girls also work in Richmond Hills and Woodbridge so they all are used to getting a $40 tips just for basic HJ at those spas. can't blame them.
The way I see it , if you break it down, $40 tips means, $20 for the massage and $ 20 for the HJ. $50 tips means extra $10 for a bit of roaming hands. $50 tippers are their fav customers.