I think the problem is that 80% of bike mechanic jobs are really not that difficult or skillful at all. Mostly it's just turning an allen wrench or changing a flat tube. It's somewhat similar with car mechanics, but car's are much more popular and common, so car mechanics will always be able to find people to pay high prices, and there are a lot more specialized jobs. It's not like being a doctor or a lawyer where you are in a regulated profession that requires years of education. So you are always going to have people willing to do it cheaply, and that means you are not going to have well qualified people sticking around to do it for low wage.