Louisiana Purchase was $15 million in 1803.
Alaska Purchase was $7.2 million in 1867.
Inflation puts $15 million in 1803 as being $19.6 million in 1867. So that puts Alaska purchase as 36.6% the price of Louisiana purchase. Honestly I can see why it was seen as a folly when the land couldn’t really be settled, crops couldn’t grow there, and the value was fur and fishing. (Though yes Louisiana as seen as a bargain).
This may not have made sense at the time, but isn’t Alaska a good source of oil?