Yeah, it depends if you want modern/efficient hardware. If your energy budget is unlimited or your performance needs are flexible, then old surplus servers are the way to go. I'm running 3 myself. But if you want anything modern, prices go exponential for the same capabilities.
I personally think everyone should be running ECC RAM, RAID storage arrays, UPS backed up equipment + networking, with full redundancy for the entire IT stack... But then again my home setup is probably overkill for home use