Zero Alaska experience here, but I consistently see $10,000 tossed out as the cost of a trip up there. From the time you leave home to getting back home it's typically three months - with two actually being spent in Alaska.
I'd be interested in a response, though, from one of those really frugal RV'ers that specialize in budget travel. Just how much could be shaved off that $10,000 with lots of effort?