Since I was born after the Apollo program, it came as quite a shock to me to find out how much the United States spent on the Apollo program and the space effort. Truly staggering amounts. Here's a plot of space spending for the last 40 years in relation to our economy (measured by GDP).
At the height of the Apollo program, 1966, about .75% of the economy was devoted to it. In today's terms, that's about $80 billion! While I am a supporter of the space program in many configurations, I am glad to see that we aren't spending that kind of money nowadays.
This sheds some light on how the 60s generation viewed space. With so many resources devoted to the effort, they could believe that the large-scale exploitation of space was right around the corner. Things could not have changed more to nowadays, where NASA can't scrape up enough money for a new launch vehicle. I'll talk more on that at a future date.
Sources and background: The source for the historical outlays is the FY '03 federal budget. Please note that the federal government historical outlays are based on a fiscal year that begins 3 months before the calendar year, while the GDP figures (NIPA Table 1.1) are based on the calendar year. For the sake of simplicity in presentation, I divided the fiscal year outlays by the calendar year GDP, although I note that this will most often understate the percentage slightly.
Some put the spending as high as 1% of GDP in its heyday, but I can't recreate that figure. Please note that my calculations are just NASA spending on space. There is a parallel "black" air force budget for space, which I guess about equals the amount spent on NASA. But I think there is a lot of intelligence money wrapped up into the air force figure--I am not going to hazard a guess about how much is really space-related, but would be happy if some knowledgable person could shed some light on this. Anyway, perhaps this is where the 1% of GDP figure comes from.
Please see the underlying spreadsheet for the calculations.