Amazingly, until last month the 2014 Mini was still available on Apple's web store for $500. Add in the fact that aside from storage it was not upgradable, and you had a computer that left a lot of users unhappy.
This meant it was actually slower at some tasks than the computer it was supposed to replace. After offering quad-core CPUs on the 20 editions, the 2014 model was stuck with a dual-core CPU. Its last update, in 2014, was disappointing.