At 85 Rc you'll get around 90k, 100k if you're lucky per hour. Work out the xp you need to get the level you want, then work out a price per hour. *If quoting something like this you should always say 'price subject to change' purely because spawns are random*
also for 84-85 rc you should expect around 80k xp/hr or there abouts. Reason it goes up at 85 is because you have access to a new platform and you should run a different area of nodes.
Oh, and at lvl 90 you get access to living souls, xp goes up from 90k on average to around 100k.
Hope this helps, although i'm probably too late replying.