I've debated buying a NUC, but at least on Intel's website, buying just the board cost somewhere in the neighborhood of 500 USD; for that price I can buy 10 Raspberry Pi 4's or ODroid XU4s. Granted, in order to use them to their full potential, you end up having to learn a lot about distributed computing (which is a bonus for geeks like me, but maybe not most people), but if your goal is to use it as a server, the NUCs seemed a bit overpriced to me.
That said, if anyone is looking to stay within the x86/x64 family of CPUs, I actually recommend looking for a used Wyse/Dell thin client on eBay. You can often get a decent quad-core system with USB3.0 and 4-8gb of RAM for around a hundred USD.
