Hi I did get it fixed but I never got the chance to sell it as it rolled off of my local garage forecourt into the brick wall across the road, electro mechanical handbrake failure caused by a voltage drop on the battery which is another favourite trick of the cars from 2014-2017, no the price you have been quoted is not normal as I never paid more than £1600 for the cooler unit to be replaced bearing in mind you could only get the parts from Audi at around £700, now you can get aftermarket parts around £450, my advice would be to get the adblue mapped out and then the cooler fixed as cheaply as possible then get rid of it ASAP, beautifully made car body wise and a joy to drive BUT parts are ruinous price wise and as mine was used as a cab frequent, got a Passat estate now not as glamorous but is as nice to drive and any parts are about a third of the price.
Steve.