There is no issue with compatibility, they're just ripping you off because it's officially 'Macintosh compatible'. Dual Hard Drives: The 2012 Mac mini has a second SATA socket on its logic board and plenty of room to install a second 2.5' hard drive. You can upgrade the drive up to 2 TB to expand your storage. Quick edit do not bother buying those OWC SSDs linked above you can get something for half the price, even quality SSDs like Samsung EVO or Crucial MX. Hard Drive: A 500 GB hard drive came standard with the late 2012 Mac mini. Mac mini fans recently rejoiced after Apple updated the storied compact Mac after two years without a major. Very practical option, and cheap SSDs these days are good enough for 98% of people. Im looking to replace a drive with unfixable SMART errors, so Ive asked my local repair shop about trying to install a WD Blue 500GB SSD on my Mac Mini (late 2012, OS 10.11.6, but building a Sierra bootable flash drive for the reformat/reinstall) - and they were rather firm in saying that trying to install anything other than an Apple SSD is. New Mac mini restricts RAM and storage upgrades, but hints at PCIe SSD possibilities. I second the above comments to install another internal 1tb or 2tb SSD. Considering that the protocol that most 2.5' SSDs works over is SATA3 which is a 6Gb/s bus. Finally, I decided to upgrade my current Mac mini (Late 2012) to replace the hard disk drive to a new 512GB SSD this week. I ordered the minimum configuration MacMini expect the processor, but I had to cancel the order after I knew that I couldn’t upgrade the hard disk myself. In most makes of Mac Mini you cant upgrade the processor - for models released since 2009, processors have. This week, Apple announced a new Mac mini. USB3.0 (5 Gb/s) is fine, USB3.1 (10 Gb/s) is better, Thunderbolt 2 (20 Gb/s), great, but you probably couldn't even tell the difference. 2012 MacBook Air: SSD, Trackpad, Battery. Copying gigantic continuous data such as video files would show some improvement for the added bus speed.

Yes, but I would argue that any noticeable different would be workload-dependent - small random files won't see you ramping up speed to full potential of the disk, let alone the bus.

Late 2012 mac mini ssd upgrade