Just a few more thoughts on campground costs for an Alaska trip.
Staying in Alaska stste parks and Canadian provincial campgrounds can get expensive. In 2013, Alaska state parks were $15-20/night without hookups and often without a sanidump (and those with a dump charged $10 extra for the privilege). BC provincial parks were $16-25/night (Canadian $), also without sanidumps and many without water. And those provincial parks with a dump also charged $10 extra. So, you may pay as much as $30-35/night for a state or provincial park without hookups. Staying multiple nights and dumping once slightly reduces that rate. But, if you have a generator, don't forget the fuel cost for providing your own nightly power.
For that reason, many RVers willingly pay $30-35/night for a private RV "park" (ie., a gravel parking lot) that comes with full (meaning 30A electric) hookups or W/E + sanidump.
Using the few US campgrounds in Alaska (National Park, Forest Service, Fish & Wildlife Service, etc.) can reduce those nightly costs if you have a Senior Pass. For example, the Denali Park campgrounds were $22/night with free water and a paved, multilane dump station, but were $11/night with the pass. Kenai National Wildlife Refuge (Hidden Lake CG) was $10/night with water and a dump, but $5/night with the pass. The Tenderfoot Forest Service Campground on the Seward Highway was $18/night with hand-pumped water and no dump, but $9/night with the pass. And Tetlin National Wildlife Refuge (Lakeview CG near Northway) was free, with or without a pass, but it was completely dry camping (don't believe the Website that says it has water!).
A boondocker's best friends in Alaska are gas stations that offer a free dump with fill-up and the Fred Meyer stores with free water and dumps (and free parking lot camping in some towns).