If you look at a parts breakdown, $600 isn't to bad. The housing of mine wore through on the bottom, and I looked into replacing just the housing (after repairing it for several seasons). It was only $150 more to get the entire Powerflow head with turbine, pulleys, belt and mounting bar. It would have cost almost $875 to have bought those separately.….. the power flow unit that will not. They are about $600.
I still have the old one, it still works, just not as efficiently. PM me and I'll send pics to show you the worn parts, if you're interested in it.