With a decent team you can crank out 2+k zombies per hour per person. (probably more if solo, but no fun)
So you're looking at paying someone for up to 50 hours. However, it would be 50 hours of fun assuming the person likes zombies, so I would price it around 5-10k fg or so minimum... if you can even find someone who'd actually enjoy doing it that is.
This post was edited by DeadlySanity on Mar 24 2013 01:15pm