Is there some overwhelming technical problem with replacing a Priv screen please?

All screen replacement services are MASSIVELY expensive (the LCD alone seems to cost $180) and places like ebay are full of Privs on which the owners seemingly cant replace their cracked screens?

Curiously, ebay sales are rife with digitiser offers, - where the digitiser cant actually be replaced because it cant practically be separated from the LCD! What is going on?? On every other cellphone the repair cost nose-dives when the phone stops being current!