I remember last time I was working for a large corp, there was this one guy on the team who was really, incredibly good. Easily worth 5x me, in terms of work done. He made 20% more than I did. There was another guy who was probably closer to 1/5th my productivity. He made maybe 20% less than I did.
the thing is, determining productivity is difficult; but I think even allowing for a high margin of error, you could sustainably target only the best, and pay twice what the competition does.