About £100,
I don't buy all dlc, and I'm getting picker, but I have bought all the dlc for Assassin's Creed 2 and Brotherhood, Mass Effect 2 and 3, Dragon Age II, Skyrim, Fallout New Vegas, Saints Row 2, 3 and 4 and other bits n pieces.
Some have been great and added alot to the story (Mass Effect and New Vegas) Some have been silly but great fun (Saints Row 3) and some have sucked so badly (Saints Row 4 and Omega for Mass Effect 3) But mostly I'm happy with my purchases and will continue to buy dlc if I want it.