This popped up on my typical searches. They are long in the tooth now by the Xeon E5 standards now - but for $150 for 5 servers with 72GB RAM each... almost worth picking up for just the RAM! Only catch seems to be you need to be able to arrange local pick-up in Dallas TX. Thought I'd pass on the listing for those that are local.
Dell C1100 (CS24-TY) Servers 72GB of RAM | eBay
Dell C1100 (CS24-TY) Servers 72GB of RAM | eBay