I've got a buddy who drives one of those! Amazing machines, but holy crap they're pricey. I don't remember an exact figure, but the cutter heads generally run more than the cost of a luxury automobile.
Definitely a machine where you're paying for the speed. If I recall correctly, my buddy's daily target is around 400-500 sticks down, limbed, and cut to size.
He mowed them down first so they couldn't complain! ;^)
I have been on a logging site in North Carolina that used one of those type of feller processors and it is even more impressive. They had another machine that had a circular blade at the bottom and arms above it to grab a tree and slice through the bottom of the trunk at the same time. It could take down a 1m tree with no effort. They also took down a cypress type tree that was easily near 2m by cutting one side than the other... In about 45 seconds. It was incredible.