Half a phone? The screen repairs are like $100-200 depending on your model, while the new phone is over $1000. It's also not just the glass, when you get your iPhone screen replaced, they replace the entire front half of your phone, basically everything involved with the display, and put a new front on. So I think you are pretty wrong here, I think they charge less than half the phone, and you actually get half of a new phone.
I get that it's a lot of parts, but this is the most fragile piece of the phone and Apple would be wise to take a note here from their competitors and explore other options. There is no reason why it needs to be a lot of parts replace to fix your cracked screen, or even have a screen that cracks at all, other than a lack of imagination in the engineering department.
