An OptiPlex sat at Goodwill for weeks, untouched. It would soon go to a landfill. I had wanted a desktop for a while. I decided to go ahead and buy it. I meant to sell it on eBay. Nobody bought it.
The computer worked once it had 8gb RAM and a hard drive. It is now mine, and I am typing this story on it. It works very well now. The i5 3570 is still very capable.
Those old desktops you see at thrift stores still have life left in them. Consider restoring one if you want a cheap desktop, a backup, or one for your child.