If you do it yourself? The glass, the LCD screen, the touch screen, possibly the LED panel (IOW, the whole screen) and anything you damage in the process (which, for people without experience in working on cellphones, is usually quit a lot). And then even more when you try to fix what you broke the first time.
The cheapest solution usually turns out to be to bring it to a good shop and pay to have it repaired. Then that's all you end up paying for.
Once you start "repairing" a cellphone, a lot of shops won't even take it for repair, because they know you'll never pay the diagnosis fee (which is hourly - as long s it takes to find everything you broke, which can be days), then you won't pay the repair bill, which can come close to the price of a new phone, so all they get is a fight, not money. Then you end up buying a new phone. It's MUCH cheaper to pay a shop to replace a screen.