Yes lawnmowers can be a real waste of time to fix. When I work on them I make sure it's a good repeat customer that doesn't mind spending money. Or it's an expensive mower that's worth sinking time into. And on stuff like that bill by the hr. There are many times I wouldn't want to hire myself
My grandfather was an electrical engineer that would custom repair and replace parts for industrial factory machinery, he could have charged a lot but seemed to take false nobility in not doing so. If a company exists to ruthlessly compete - charge what you can, deny work, or they take you for a ride