If you build a winning franchise you can attract and retain free agents (and draft picks) for fair value if you establish a winning franchise like McBeane has done. Milano, Poyer, Hyde, Dawkins, and White are pry the best examples of this. The problem is you're not always going to have a winning culture and you're going to have to overpay for free agents when you don't (Mario Williams, Derrick Dockery to name a couple).
Crappy weather and a less than desired Buffalo night life will always count against the Bills when it comes to attracting free agents. Being able to play indoors would help a little.