How on Earth MacMini with 8GB of RAM and i7 CPU is underpowered for the use? It is underpowered in only one way - energy consumption is so low that there are even server farms built on MacMinis, and colocation services targeting this brave little server.
You get a custom operating system that literally no one else offers. It is a bit hard to put a price on that, but to me, it's absolutely worth the money they ask for the mini. I would even risk saying it's very cheap for what it offers.
