The U.S. purchased Louisiana from France for $15 million in 1803. The U.S. purchased Alaska from Russia in for $72 million in 1867. If you project $15 million and $72 million into 2026 dollars you then have to ask is Greenland worth as much as Louisiana and Alaska in today's dollars. I say it's worth less than either. That's how I would negotiate this purchase. It would be good if we could hire William Seward to negotiate the deal, but unfortunately he is dead.