You can still buy a pristine 13 mini on the secondary market. The original iPhone is not a viable device today, but the 13 mini is better across every tech axis (better processor, battery life, screen, camera, ...) than the SE and is worth comparing to.
This is missing the point. I have a 3rd gen SE and am not currently in the market for a new phone. The issue is that Apple is no longer selling anything to people who want a small iPhone. Moreover, the used market will dry up eventually, and iOS support will be dropped even sooner.