If you are looking for used corney kegs at a fair price then you might want to check out keggle brewing. I have ordered from them 3 times and have found their prices and quality of kegs to be very competitive. This last week I received 4 ball lock corney kegs for $30 each plus shipping. This came out to $38 per keg including shipping and the quality of the kegs I got were great. Just thought I would mention this as a possible alternative to other sources.
http://www.kegglebrewing.com/Reconditioned-Ball-Lock-Kegs_c_18.html
http://www.kegglebrewing.com/Reconditioned-Ball-Lock-Kegs_c_18.html