When I was young I cut a lot of grass with el-cheapo mowers. Stamped sheet metal deck with a tubular steel handle. 4 little wheels bolted to the corners of the deck. (the "good"
ones had bearings and the "regular" ones had plastic centers). A 3.5 HP second generation Briggs & Stratton engine and a blade. The "high" quality mowers had a throttle control mounted on the handle; this usually broke after year or two and you disconnected the cable at the carburetor and used the lever on the carb to set the engine speed. No dead man switches, No safety cutoffs, No blade brakes of any type and you provided the propulsion. I still have all of my fingers and toes.
There was a contact on the throttle lever that grounded out the magneto to shut off the engine. If you pushed the lever beyond the "stop" detent the engine would not shut off. Eventually that function would just break completely and engine would not shut off until it ran out of gas. With those mowers you just carried a plastic handled screw driver in your back pocket and used the screw driver to short out the exposed end of the spark plug to the cylinder head to shut off the engine. It was important that you didn't use a wooden handled screw driver because damp wood isn't a good electrical insulator (voice of experience here).
The sheet metal deck would rust apart long before the engine would give out. It was cheaper to just buy another mower when that deck gave out. Then you had a spare engine, blade, handle and maybe a wheel or two. Craftsman mowers used slightly thicker sheet metal for the decks and would last longer than the K-mart mowers. The K-mart mowers cut the grass just as well and they were about 1/2 the price of the Craftsman mowers.
A carburetor kit for a Briggs & Stratton consisted of a couple of gaskets and a fuel diaphragm. It cost less than $2 and took about 15 minutes to install. The "I guess .......air filter?" was a piece of foam that you washed in gasoline. I don't recall ever buying a new one. You washed the one you had until it fell apart and then you stole one off of one of the spare B&S engines you had laying around.
If you hit a rock, stump or tree root and the blade stopped abruptly the Woodruff key between the crankshaft and flywheel would shear. The magneto would then be out of time and the engine wouldn't run. You had to pull the flywheel off and replace that key. That job was a PITA and sometimes the flywheel would be cracked at the keyway - That's when that second engine laying around was useful.
I look at these $400+ lawn mowers today with the safety devices, cast aluminum decks, OHV engines and all the other upgrades and I know they are far better tools than we had when I was young, but I'm not sure they are a better value for the money.