The title doesn’t accurately describe what was said. Greenland is still not for sale, Trump will still not be able to bid on Greenland, but they are open to let the US build bases, mines and trade ports or whatever it needs (while paying the Danes, of course) and leave them alone, which is probably what was going to happen anyway.

It remains duly noted to all Europeans that a US president elect threatened a European ally with a military invasion, and that is something that all Europeans should keep front and center whenever we think of the US.