Cell Blades
"A base QS22 blade with two Cell chips and 8 GB of memory costs $9,995, which is about four times the cost of an x64 blade"
... or you could buy a PS3 and turn that into a "blade server". Of course, it only has 1 Cell processor, but 2 PS3's are definitely cheaper than the blades. Of course, you're stuck with 256Mb RAM.