True, it has an low clearance height but with independent suspension that's not as big as it is with live axle 4x4's. As for maintenance, yes its expensive but in reality who would want to take there Cayenne off-road? Seriously i won't...
As for professional off-roading, for them (Rally Teams) money is not a object because all comes from the sponsors and private financiers also prize money, you know those Evo's and Subaru's which run for rally's, their tranny's cost around 100k euro's brand new! :P:) Crazy Stuff man! hehehe