I am guessing that that seller isn't terribly sophisticated - he apparently doesn't realize that AK and HI are in the U.S. - if he wanted to be clear he should have just said he only ships to the continental U.S.
Given that - there has always been a myth that shipping things to AK/HI via USPS is much higher. It just isn't. Private shipping is another story.
There was a time when contactors would sometimes ship things such as bags of concrete and building blocks via the Post Office because of a loophole in regulations made the Post Office the cheapest way to go.
https://www.washingtonpost.com/archive/politics/1990/07/30/parcel-post-paying-the-freight-for-alaskans/467be7cf-8962-41b2-804a-6e31c5e14d34/