New computers are fairly inexpensive now, but refurbished computers are the cheapest of all.
Refurbishing carries with it the idea that somehow the computer has been rebuilt because there were serious problems. In fact, this is almost never the case, not least because rebuilding would usually cost more in labor and parts than you could get for the computer.
Dell, for example, has long had a policy of taking any computer that’s been returned and marking it for sale as refurbished, even if it’s never been out of the box. Why would it have computers returned that had never been out of their shipping boxes ? Well, schools and businesses and government agencies often order more computers than they actually need and so they send the extras back.