Ring Apple Care, show them evidence, i had a 21" iMac screen replaced once that was 2 years out of warranty. Be nice.I have the same issue on my iMac 5k (late 2015) .. contacted a local authorised repair shop and they asked for €700 because my machine was out of warranty. They said that this is a problem that is not so common thus no free repair program from Apple.
Not so common, huh! I don't think so.
I'm starting to get more and more frustrated with Apple lately.
And yeah.. I've switched to an Android phone, stupid Apple.