Here is the guy's email address that I buy my steel from:
AR 500 wholesale cost is about $25 bucks a square
AR 550 is about $40 and AR 600 is about $80
I think I paid $170 bucks for my 16 inch AR600 with ears cut in it so you can hang them on chains without drilling it, which would be very Hard or welding it which damages the hardness.
I can tell you I love the targets and have been back to by different sizes from the same guy twice.