I mentioned this on another thread, I was asking my regular girl at S9 (who is now permanently retired and long gone), about the tips. She straight up told me she doesn't charge anything extra. She said "I'm happy with whatever they give me, and if they don't give anything I'm happy that they come see me". She said she would always do cbj for free. Now, after reading her reviews, I know she did bbbj and cfs with some guys and knowing her and given what she told me, that would have been free too. So everyone that tipped her $50 and $100 was just really really nice because in her mind the charge for doing that was $0.
Personally, I'm somewhere in the middle about this. I think if the girl does what is considered extra and has the attitude "I'm just happy that they come see me, no charge" then thats her choice. I wouldn't tip 50 or 100 in that case, but give her something if she did a good job. Thats the happy middle ground for me.