I have literally gotten as much done in 4 hours as anther teammate did in 2 weeks. (Fixed the same bug.) However, usually we don't have direct comparisons.

I wonder if breaking a team down into 2 sub teams that compete over 2 week periods to fix the same bugs might be an interesting solution. I suspect most people would be more productive, but less than twice as productive. However, you would then be able to directly pick the "best" output which could be vary valuable. Add in the ability to discover and drop unproductive people and you might have a net win.

Edit: Ok, you might also create a hostile, environment that is so stressful you force the most productive people to leave.