I really hate questions/threads that start with "is it worth....". Worth is such an arbitrary metric, especially if the system in question doesn't generate money.

Is 10 fps extra worth $700? Maybe for that person's e-peen. 

Maybe you get 50% speed increase for a render, so instead of the job finishing at 5 AM, it finishes at 2 AM, and so you're asleep anyways and it doesnt matter.