Is this really true? Getting to the moon cost 4% of the federal budget at peak, and from the graphs it looks like about 2% of the budget on average, for 13 years [1]. I'm fairly certain that Columbus' voyages cost nowhere near a percentage point of the economic output of all of Europe for a decade. But maybe I'm wrong. Could you provide a citation?

Also, as I understand it we're fairly certain of the economic value of other planets given our current technology (not much). So that aspect of Columbus' voyage does not apply today.

[1] http://en.wikipedia.org/wiki/Budget_of_NASA#Cost_of_project_...