Why the Greenland acquisition plot does not look all that fantastical

Why does the plot of acquiring Greenland not look all that fantastical? One need only recall the history of the United States and its bargain purchases.

In 1803 Louisiana was bought from France for roughly 15 million dollars. As a result, its territories went, wholly or in part, to form: Louisiana, Arkansas, Missouri, Iowa, North Dakota, South Dakota, Nebraska, Oklahoma, Kansas, Minnesota west of the Mississippi, eastern Colorado, eastern Wyoming and eastern Montana.

In 1819, under the Adams-Onís Treaty, Florida was acquired from Spain for 5 million dollars.

In 1845 Texas was annexed on condition that the United States assume its public debt; that is, the acquisition came about not by purchase but as a paid-for political absorption.

The Mexican Cession of 1848 cost 15 million dollars plus the cancellation of further debts. It went, wholly or in part, to form the states of California, Nevada, Utah, Arizona, New Mexico, western Colorado and south-western Wyoming.

In 1853 came the Gadsden Purchase from Mexico for 10 million dollars, and Arizona grew by its southern part, as did New Mexico.

In 1867 Alaska was bought from Russia for 7.2 million dollars.