Cost to repair iMac glass screen 21.5"at Apple store

Can anyone please tell me how to get an estimate of the cost to replace glass screen on iMac 21.5" late 2015 LED backlit, retina display? I made an appointment at genius bar but have tried to contact the local store 5 times. 4 of the times I have been routed to tech support, 2 of which I was told I had to contact the store directly, 1 of those sent me back to tech support because the local store does not answer. I do not have Apple care and there is no information available as to the part needed or the cost of labor charge at Apple. I contacted a computer repair store and they quoted me $700.