I can verify that these places are accessible, and that the permafrost extends quite a bit farther south than one might expect. I used to live just south of the Yukon territory.

There are regular long-haul trucks that go up there all year round; if you go in winter, you can use an ice road to get to the very cold and remote places. Given the regular volume of traffic, I'd say the cost is not prohibitive. I can get precise figures if you'd like.