It still doesn't include a monitor, keyboard and mouse.
Those are called laptops. Yes some manufacturers throw in a keyboard and mouse for free but few throw in a monitor for free unless it's an all-in-one. Mini PCs generally do not include keyboard, mouse, or monitor. At my company there were bins of keyboards and mice in the computer supply closet that no one used. I think you can buy them used by the pallet.
The original assumption was you'd just use the peripherals from your previous machine, but macOS doesn't support subpixel font rendering, so text looks pretty bad on 1080p monitors (which are still surprisingly common)
That's your opinion that they look bad but the main reason Apple disabled subpixel font rendering since Mojave (2018) is that does not look good on higher resolutions displays like Retina.
Then there's the keyboard, which unless your previous machine was a mac, you'll probably need a new one of those, too.
Why? Unless your ancient keyboard uses ancient 5 pin DIN, USB keyboards works. I've plugged in Windows keyboards into Macs and they work. Sure, the mapping of certain keys is different but I don't need a new keyboard.
That just leaves the mouse, which kind of seems like punishing yourself if you've replaced everything else.
Again why? Any USB mouse works. I've used Dell mice with Macs, and, again, they just work.
$900 is a far cry from the total out door price you'll be spending.
Have you actually used USB keyboards and mice with a Mac in the last 30 years because it seems like you have not.