depending where you go if you go toa place with dynopacks with the hubs it might be slightly more cause they have to take your wheels off but like sme places e.g. 999 i know that they have the dynodynamic (or what ever you call it) they have the rollers for all four wheels and i dont see how i would cost heaps more to just extend their ramps like 30cm or what ever so that your front wheels will sit on the rollers, its designed for that.
But im pretty sure power runs at 999 around 50-80 still even if its not a dyno day. but if you really want to find out why dot you just call them upand see how much a power run will cost ya.