A lot of what any government does is a rounding error on the overall budget, but are still absolutely vital. Those rounding errors don't half add up quickly. I'm pro-space exploration and believe it's worth funding, but this particular argument doesn't strike me as useful. Space exploration and technology development should justify it's costs on the same basis as any other government programs, any number of which of which could be revolutionized by 'small' increases in the overall budget.