Even using your numbers, aren't you comparing apples and oranges? Isn't the economy generated coming in private sector dollars? The expenditures in public(govt) dollars?
Yes, the economic benefit coming in is private sector dollars. Where do you think tax dollars come from? Private revenues maybe? What supports local economies? Private revenues maybe?
Think of it as an economic stimulus package that has incredible side benefits in terms of quality of life to the citizens of the U.S.