I thought you were looking for an axle with disc brakes as well? I paid $200 for my Exploder 8.8 with rotors, calipers, e-brake cables,sway bar, 4.10s, and an open carrier (I plan on going with a locker).
A good price for that would be a $100 but I would probably pay $150 if its in good shape.
I know junkyards around here (u pull it) have specials on certain days that axles are only $50 no matter what axle.