Let's suppose that it is easy to buy a legislator. The problem here is that there's also lots of money being used to sway legislators towards increased security, so you'll be in a bidding war.

Care to elaborate on a few such cases?

It can be insanely profitable. NPR on how some lobbying efforts yield returns of 22,000 percent:

http://www.npr.org/blogs/money/2012/01/06/144737864/forget-s...

Look at how much Hollywood paid to Lamar Smith for SOPA:

http://www.opensecrets.org/politicians/industries.php?cycle=...

It looks like the going rate for a Congressman who is a powerful committee chair is around $100K.

A rank-and-file Congressman can usually be had for $10K or so.