Pair programming can be amazingly effective, however you shouldn't be hiring programmers in pairs. You can't force developers to pair program. It only works when two developers click and decide they can learn from each other and build something awesome together. My advice is to hire as many of the smartest developers you can find and put them in a setting that naturally lends itself to encouraging part-time pair programming. Developers need to be able to code alone, but also talk to others on the team about it.
Finding the right mix that works for you and your company will be more art than science, and certainly not something you can do by blindly following the demands of some published methodology.
That said, the more bugs you squash before they ever get checked in, the more you save in the long run. Having another developer looking on as you architect something will always be more effective than having a tester black-box it afterward. I'd call it money well spent.
