Don't forget that the 9600 repair bills most of you speak of were 10-15 years ago. A lot of the parts would now be close to double in price and the same goes for dealer shop rates. Maintenance costs on both walker and STS machine is similar today.
One area that has been expensive to maintain on walker machines recently is the feeder house drive, specifically the reverser gear case. Most of the machines that come here for inspections run an air reel or wind system on the header which uses 25-35 hp on top of what the header itself requires and these gear cases just aren't capable of it year after year. It's to the point that I'll keep a reman gear case in stock because they fail so often. STS's don't have these issues due to most of them having the HD setup with the oil cooler. Synthetic oil is all that's needed.