AS2023

Hi all I am after some advice if that is possible, I have a 2017 TDI Q5 and have just put it into my local Audi dealer because it has an ad-blue fault warning message appear on the dashboard, Audi have just called me to say that it is a sensor fault but because the sensor is integral with the pump and tank the cost to replace is £2400 plus Vat, I find that a huge amount of money considering that the whole Ad-Blue system was added to all VW & Audi Diesel cars because off the emissions scam, I was hoping that because these systems were never originally mean to be on the cars and therefore the whole ad-blue system was an after thought that Audi may cover it with an extended warranty, but they are saying not. Does any one have any info or advice? Thanks Andy