How much does Apple charge to fix small hairline cracks?

I have a very very small hairline crack at the top of my iPhone 6s. It's not noticeable but I can notice it. I just wanted to know how much it would cost to fix it.

Whatever they charge to replace the entire casing/body of the phone. They don't "fix" cracks, they replace the entire component that is cracked.

So, look at several hundred dollars as a place to start.