I own 4 Alpine Grinders and have been using them since 1995. There is a learning curve on these units and you will consume a lot of teeth until you learn how to run them. I live in rock bound Southern California and only change teeth about once a week. I do touch them up frequently with a angle grinder and a diamond wheel. My original unit from 1995 is still running and is used as a back up unit.
I have no idea what the other gentleman is breaking that is costing him so much money as mine have been rock solid. We do however service our units on a daily basis. The nice thing about the Alpine is it will grind stumps just about everywhere other grinders won't.