Some AK mags are quite collectible like bakelite Norinco mags, North Korean stamped, Bosnian fleur de lis or two rib, etc. If they're generic Euro steel mags you could get $40/piece but much like SKS-D prices lately, sellers think they're worth twice that. They're not, and the constant BTTs indicate no one sane is paying those prices.
I bought eight pristine East German 5/30s recently for under $50/piece and that was a bit high. Zahal.org has pledged to ship us pinned AK mags in anticipation of the new sporting rifles rumored to be coming soon, and Euro steel mags in the States are anywhere from $15-30 depending on manufacture and condition.