I've been looking around for a good place to pick up a used or refurbed Mac Mini. I'm amazed at how expensive the used and refurbed Minis are. I would have assumed used Minis would be down to 200-300 range, but I'm not finding that anywhere.
They are very popular hence the high price. Most of Apple's refurbs are priced at a percentage discount of the new price so sometimes strange anomalies pop up like a Core Solo combo drive mini coasting more than a Core Duo superdrive. Apple refurb site is generally the best place to pickup a quality refurb mini with a full warranty. eBay would be the most expensive place. craigslist might be lucky for you.