It depends on the WG's mentality...
Some charge extra for everything so I find it bizarre to tip such an SP.
Others let you do whatever you want to with them reasonably so in the heat of passion leaving you feeling compelled to tip without her asking and that's not all since they leave you feeling so amazingly super fantastic that you plan on revisiting with a special gift.
SuperFuck style...Book another hour right after and another thereafter and why not a fourth hour?
I tried tipping but my money is often given back to me. Then you get those SP who ask for a tip yet the session was so awefull and you think to yourself...
?????????? WTF ??????????
Other punters tip R90
000.00 ... Seriously.
I was going to say go with whatever you feel but considering the R90k let me rather not say.
Others will give you a better idea shortly.