The chain gun on an A-10 Thunderbolt (aka Warthog) files about 3900
rounds per minute. Another way to say it: $24,375 per second of
depleted uranium rounds. But don't hold the trigger for more than 18
seconds because the barrel will melt.

A-10's don't have a "chain gun"... maybe you're thinking of the AH-64
Apache? The A-10's magazine would empty long before the barrels
(plural) "melted". The GAU-8's biggest limitation besides ammo supply
is that the recoil slows the A-10 quickly, and gasses from the muzzle
get sucked into the engines while firing. Besides the high cost of DU
ammo, there's an environmetal issue with dust created by projectile
impact. Scary stuff.