I've never been to a gun show that didn't have plenty of 9x18 for sale.
The cheapest you're going to find right now is made by LVE Novosibirsk in Russia and is going for $175 per 1,000 rounds, plus shipping of course. With shipping to your door, you're still paying under ten bucks for each 50 round box.
Aside from the other deals listed, Military Shooters LLC has 500rds of Brown Bear for $98.49 plus shipping. http://www.dealerease.net/catalog/product.asp?pid=1028170&ret_id=140211
Military Shooters LLC has Silver Bear for just a few cents more. Silver bear must have a different powder or something because it gives the gun a different smell after you're done shooting.