OK, let's do some quick math.
$58 / 12 each = $4.85 per mag retail.
ProMags, arguably some of the worst mags on the market, are 4 times that on sale at Midway USA. Do you really want to trust your $500+ firearm to a couple of dollars worth of suspect metal?
"The 1911 was the design, given by God to us through John M. Browning, that represents the epitome of what a killing tool needs to be. It was true in 1911 and it's true now." - Col. Robert Coates commanding, U.S. Marine Corp Special Operations Command Detachment 1 (DET 1)