I know nothing about this RM but from my experience with other RM, the rate depends on multiple factors such as the proposed activities, when and where, & how long a session as well as factors we are unaware of such as the RM's particular need for $ at the moment and his schedule (personal, professional, etc.)
If I am interested in a RM, I messenger him on RM, telling him about me (age, height, etc.), what I'm looking for and for how long and then propose a donation. This usually always works. I propose a donation that I think is fair, even if a tad high. I don't want to get into haggling with the RM as that can create a bad vibe if a bargain is struck.