An antiquated 8 year old refurbished Apple computer for $300. You can buy a more recent laptop running Windows 10 for under $300 with better specs.
This one can actually be upgraded to the latest os and 16GB RAM and a big fat SSD. I have the i7 and it’s terrific, but I use it for development and testing. I believe the Late 2014 model is not as upgradeable, but I could be wrong.
the price might seem a little high. But I’ve been running this exact same model since 2013 at an HTPC with no problems at all. I still get updates, and, mfeferman points out, you can update this one VERY easily. And it’s just a bloody beast. Again, mine has been on for… lessee… roughly 64,000 hours with the only power downs being when the power went out. And it’s still chugging away just fine. Recent != better.
THAT said… you can sometimes find these at comparable prices on certain internet-based auction sites. But those are always a roll of the dice… unlike Woot refurbs. Which are only NORMALLY A roll of the dice.
Also, mfeferman is correct again that the 2014 model Mini was no where near as upgradable as the 2012. They really ruined the system after that.
One alternative you could look at is using the Intel NUC for a much better $500 or so alternative. HOWEVER… Hackintosh systems are not for the faint of heart. You do need to do some work, and you DO need to be careful with Apple’s attitude towards upgrades and controlling their users.