I would still consider that demarketing, but I applaud your effort in trying to control quality. Sometimes it's impossible to find qualified help or help that you can train to the standards that you expect. That's what I ran into as a software developer and publisher about 15 years ago. There is no one here that I know of who doubts your expertise and/or the quality of your workmanship.
There is truly both an art and a skill involved in fixing small engine equipment. Many mechanics can work on the big stuff, but most of them who can will leave the smaller equipment, such as chain saws, to others such as you and a few other trained mechanics who are willing to tackle them. Here is an interesting point: a new Stihl chain saw may be the most expensive common lawn and garden piece of equipment that there is when measured in $/lb. As such, that would also explain why it is one of the most frequently stolen.
