Despite Denmark’s repeated insistence that Greenland is not for sale, U.S. President Donald Trump and his team are “talking about what a potential purchase would look like,” according to a White House spokesperson.

But even as a thought experiment that assumes the presence of a willing seller, discussion of the hypothetical sale of an autonomous territory such as Greenland rapidly encounters imponderables such as how a meaningful price tag could even be established.

“There’s not a market for buying and selling countries,” said Nick Kounis, chief economist of Dutch ?ABN AMRO bank, noting there was no accepted framework for valuing countries.