What a bargain!
Our local recycling centre had at least three complete 486-based systems (as well as loads of Pentium/P2/P3 boxes in various states) - and these would typically go for NZ$5 or thereabouts!
eBay isn't the best place to look for old PC-based stuff - ask around locally... Someone probably has an old machine in their garage that they'd happily give you!
- Ali