how much does it cost to get iphone 5 screen replaced??

$149 USD. Make a Genius Bar appointment at your nearest Apple Store and backup your iPhone before you go.

$149, as of Jun 03, 2013.

http://www.macrumors.com/2013/06/03/apple-begins-offering-in-store-iphone-5-disp lay-replacements-for-149/

You would need to call your closest Apple Store and ask if they even do screen replacement and what the cost is.