I bought the cheapest petrol mower in B&Q when I moved into the previous house in the late 90's. About £80 if memory serves. It does have a reasonable tecumseh engine and proper carb and it's still going strong. Starts on the first pull every time, although it did get a bit troublesome once. Once I'd cleared the blocked passage in the carb it was back to its' normal self.
The wheels will fall off and the (plastic) deck will fall apart before there are any mechanical problems with it, I'm sure.
It's been relegated to spare since I caught my brother about to chuck an early 90's Yard King in the skip. Again, clean out the carb and put some fresh petrol in it and it's as good as new.
If you fancy a project, watch your local freecycle for mowers that "don't start", especially this time of year. Couple of hours and a can of carb cleaner and your problem will be solved.
When you think of how much energy a proper mower uses, then think what a cheap chinese battery can muster and for how long, you know just how much fun a battery mower will be.