Not particularly surprising for new ammo. Norinco would buy lead, copper, brass, and chemical precursors at the same global prices as any other ammo maker. Since the actual manufacturing is presumably mostly industrialized anyway, labour should make up only a tiny fraction of the cost per round.
Surplus is cheap because it's well... surplus - someone else paid for the materials and production years ago and don't want/need it any more so they sell it off for whatever they can get - it's expected to be expended in training or combat anyway.