There's no economic incentive to hire anyone below the top decile. Assuming you believe the "10x" rule (which says that there is a 10x productivity delta between the best and worse developers), I get the best bang-for-the-buck by hiring the best developer I can find.

Even if compensation did scale linearly with productivity, two programmers with productivity X are still worse than one programmer with productivity 2X since communication costs grow as the team size grows.

I wouldn't be a prudent businessman if I didn't fight relentlessly for the best developers...