Depends on where you are and where you are buying them from, also Pin vs Ball.
Pins - $40 each shipped to you from this guy that lives near me. He bought out a bottler and is getting rid of them all. I went over and got a couple from him and saved the shipping.
BigJohn and I got a pallet of them for cheap because we took the whole lot in one shipment. That was more than 5 years ago and i think it was ~$20/keg.