The Raspberry Pi has three huge advantages over those other options:

1) GPIO, letting you do things like learning to flash LEDs or controlling robotic arms and getting ready to use a Pi Zero for robots or such.

2) Cool add-ons, like the Pi Camera or AI modules, and a product family such as compute modules, Pi Zero, etc. A strong third party market of Hats, etc.

3) SUPPORT. Pi 500 is available as part of a kit with the official Raspberry Pi Beginner’s Guide, which I know from experience in teaching people interested in learning this kind of stuff, is a really awesome getting started resource. But it doesn't stop there -- Raspberry Pi Press has a lot of freely available books that teach various topics, AND a monthly magazine to teach and inspire. Not to mention countless tutorials meant specifically for Pi and Pi OS.

This is really, really awesome.

Those ebay specials aren't going to satisfy any of these. And while direct RPi competitors do provide a response to the first point, they get weak on the second point, the RPi is pretty unique in the third point.