Mowers are very simple machines. A little bit of maintenance goes a long way. I've only ever used what $50 gets me on craigslist and have never pined for anything better.

What is a disposable mower? That number is way off, checking my local hardware store a brand new mower is $150AUD.

This simply isn't true. A decent push mower can be had for about $180. Cheaper ones are about $130. Do you have a source for $500+ gas push mowers? I'd imagine they are very niche companies or models.

This also ignores the used market. Mine was used for $30.

The cheapest Honda push mower at home depot (today in the midwest) is $420, the second cheapest is $550.

They will easily go 20 years without much maintenance. Nobody I know buying $180 mowers gets more than a few years out of them and they are off to the landfill.

Perhaps they don't know how to take care of them. I have a mower that's 30 years old and another that's over 10. They are not high-end models (neither exist today to check prices). It's a shame people throw our perfectly good equipment because they can't keep it running, lawnmowers or otherwise.

If your argument is that a decent mower can go 20 years, then that excludes battery powered ones. You'll need to replace the batteries.