Our tip asks $25 for any old mower, regardless of the condition. They had to standardize their prices to stop arguments and haggling.
I always get far more than $25 value out of the parts. Maybe I've just been lucky, but every single mower I have brought home goes with just a small amount of tinkering. I am lucky that I live in an area populated by mechanical morons. The things some people do to their mowers is often beyond belief. Then they throw them to the tip and go off to Bunnings to buy another one. I could write a book on it. Maintenance and repairs are clearly foreign words to many people around here. The way people today see it, why bother maintaining anything when Bunnings is just around the corner? Just use it and abuse it until it runs out of oil and grinds to a halt. Throw it away and buy a new one. I'm amazed at how many tip mowers simply have very dirty spark plugs. Clean the plug and away they go. Or in the case of Rover mowers, the little sensor on the coil has been completely blocked off with grass and muck until it no longer works.
All of my restored mowers are either semi-retired or retired. Like retired racehorses, I give them a run every now and then, but they no longer have to cut grass. They spend their days in the comfort of the shed with a blanket thrown over them. They get only the best fuel and oil and TLC. Some smoke a bit, others don't. They all have their little idiosyncrasies. Some start first pull, others need three pulls on choke, they all sound different when they run, a couple leak a few drops of oil each week, others are not so incontinent. I sometimes think I am running a mower retirement/nursing home. LOL!