Paisley, the computer hosting this website, is sitting on a desk in our house. It cost $120.
The board is a JetWay JNF9B, which has a built in Intel Atom D2700 2.13GHz CPU. For memory, it has 2 2GB DDRs that I scavanged from my dead Macbook Pro. The main hard drive, with 500GB, was just lying around the house. The rest of the hard drives are old backup drives I had and ones scanvanged from various dead computers. The power supply was retrieved from the e-waste bin at my workplace. I laser-cut the housing from scraps. It’s nice working at the Exploratorium.