What makes a Glock so cheap?

So I saw an ad on Facebook, with a Glock 48 for $420. Is that a deal, and more importantly, why are they so cheap. I know shotguns can be made for less than $30, and rifles even less; but they're all far more expensive, especially when it comes to the name-brand stuff. What does Glock do different to be able to price their guns so low, and their MSRP for about $600. They're almost as cheap as Hi-Point. I've heard the quality is good, and even thought that was the reason, but I just don't see it. That's a price to produce an ammo, let alone a gun. What's their secret, and is this a good deal or an obvious scam?