there hasn't been new steel core 7.62x39 ammo in the US for over a decade. when the announcement came it was no longer importable, the price went up on available stock like a pre-89 ak-47!.
it's short due to iraq just like 55gr .223 is.
while it is out there the price has risen somewhat.
last time there was a 7.62x39 shotage the price of a case rose 300%. but again that was due to ammo not being allowed into the us. way back when