What piece of equipment is not a money pit for that matter. Hell you break a plastic bumper on a pick up truck and it is $1000. You have to charge accordingly to cover your maintenance costs on ALL your equipment and try to maintain them properly. I have gotten 7 years out of my RG50 and SC852 and they both are work horses. I am not sure if have the numbers correct but we have put more into our chippers than our stump grinders over the years.....I do think the lower hp stump grinders are junk so if you have one of those....then yes, they may be money pits......
Why are you comparing apples to oranges? Chipper also (should) make a whole hell of a lot more than a stump grinder..