They were quite willing to sell us Alaska at the time. They viewed it as a barely populated, low value frontier outpost that would be nearly impossible to defend. If the USA wanted to just take from Russia there was little/nothing they could have done to stop it, so they viewed it as better to get some money for it while they still could than risk several orders of magnitude more plus all the dead soldiers, for land that had no apparent strategic, nationalistic, or economic (beyond the fur trade) value.