Other World Computing discounts a selection of used Apple Mac Pros, with prices starting at $499. Plus, all orders qualify for free shipping. Each item is covered by a 90-day OWC warranty. Note that for some models, available quantities may be limited. A couple of best bets, with comparisons against original retail prices:

• Used Apple Mac Pro Quad 2.93GHz Xeon Workstation w/ 4GB RAM for $575 ($2,425 off)
• used Apple Mac Pro Quad 3.33GHz Xeon Workstation w/ 6GB RAM for $879 (pictured, $3,169 off)