Maybe cheaper doesn't mean better. Last year, I was comparing career stats, and it looked like Victorino was just as good as guys like BJ Upton, Michael Bourn, and Ellsbury, and he was very close to those guys statistically.
Granderson is this year's Victorino. A .830 career OPS in center is a big deal, but even more so with that 40 HR bat. He makes the team much more flexible defensively, and could probably be worth as little at 1/3 to 1/2 the contract Ellsbury just received.