Surprisingly, these are not of great value. Don't know where you are located, but Numrich offers a case with 12 magazines for $51.45. That's less than five bucks a magazine, ignoring the case.

Magazine Case w/ 12 Magazines


I have one, and after cleaning and degreasing, it is in really presentable condition, with 12 excellent condition mags. A bargain to my mind!

Cheers.