how much does the ammo cost for the 7.26 mm minigun?

In the wonderful book Charlie Wilson's War, Congressmen Wilson learns that in war, bullets are more expensive then guns, here is an example.

A man fires around 7,000 rounds a year at 15 cents per round which equals $1,050 per person to fire a cheap $165 AK-47.

My question and I haven't been able to find the answer is how much does the 7.26 mm rounds that the mingun fire cost. This machine fires 2,000 to 4,000 rounds a PER MINUTE!!!

While this gun cost $35,000 if this ammo also cost $0.15 a round 1 minute of shooting would cost $600, that seems like it could add of fast even by US military standards