I charge the same as my fairly moderate/highish (but depends who you are comparing to!) Escort rates, however I find preparation and clean up is much more for BDSM/Domme bookings. There are also many 'subs/slaves' who are not true submissives, they are just rude, pushy, needy demanding. Genuine subs/slaves are a pleasure to find. I have spent a lot on equipment but I like the mix, it's harder in some ways but easier in other ways (on the whole harder but not the same as GFE/Escort).
Also some GFE/Escort clients combine the two.