I need a lawn mower for between fifteen and twenty five minutes every week or two. A $100 mower has lasted me many years, and when it breaks I will purchase another one. It would be a total waste of money to pay a considerable amount more for something with a brand name and an engine that in most cases is made by the same company that made the engine on the $89 machine.
If I had to cut the back forty every week that would be a different story, but there are times the $100 is just dandy.