I agree with most of what you said, but the reality is, cost IS an issue with Congress. It's a huge hurdle to overcome, not only do you require enough congressman to support a very controversial topic (controversial because they would feel they'd lose votes), but they also have to justify a fairly high cost. I'm not sure there's enough of an appetite out there for it.
Since when? Since today? The pitiful and despicable Congress is sending $18 billion of our money to buy condoms for Africa; yet you don't think they will find national security important enough to spend half that to protect our borders from an invasion? What's wrong with this picture? This is the Outer Limits.