I have a lot of old Macs that I got for free, but the cheapest one I got was a Dual 2.0 G5 for $1.25 AUD!!
My other Dual 2.0 G5 I got for $50 AUD.
Got both from eBay, set up the $50 one, plugged in an ADC Cinema Display (LCD) I got for free when I bought a cheap broken iBook, and it ran great. A while later I saw the other one on eBay with 1 bid at $1, I bid $1.5, for it for $1.25. I took some RAM out of it and put it in the other G5, but other than that, it’s been sitting here for a year and a half doing nothing.😀