A couple things:
1. Price isn't everything. Look at the quality. How are the lips formed? Nice and sharp corners, well defined? What about the spot welds? How many? How big are they? Little pin pricks, or a good solid 1/8-1/4" in diameter?
2. Steel mags. Yes they are tough. But they have three possoble drawbacks: 1. Steel can rust, aluminum won't. 2. They are heavy. 3. Which will wear faster with repeated use? The steel mag body, or the aluminum reciever? Which of those is the more expensive component? The mag? Or the reciever?
Just things to consider before you plunk down your money.