The Mac Pro is the only Apple system that has user-replaceable storage. The Mac Mini & Studio both feature slotted storage modules, but Apple firmware locks it and so it can't be replaced much less upgraded.

This is incorrect. Mac minis (starting with the M4 model) and Mac Studios simply need to be restored via DFU mode following physical installation of another SSD (be it a larger one or simply a replacement) to function. There are third parties who have reverse engineered the design of the PCB and paired it with the same Hynix and Sandisk NAND chips Apple use.

There is no firmware lock, and here's the iFixIt guide for doing it.

> How to Replace the SSD in your Mac mini (2024)

https://www.ifixit.com/Guide/How+to+Replace+the+SSD+in+your+...

You can indeed purchase third party replacements up to the maximum size supported by that model.

I would still call this practice malicious. There's no justifiable reason for that much of a jump in price in the first place.