Huge repair bill even under factory warranty

I drive a 2013 Nissan X-trail 2l petrol and at 82,000 km the clutch has started slipping, and is now close to being dangerous to be on the road. I took it to Nissan Stellenbosch, and got a quote of R17,400 to get it fixed. Now with a car still under its 90,000 / 3yr factory warranty, that is a pretty tall order. I understand that clutch plates may not be covered under warranty (and I am more than willing to pay for that and the labour), but to bill me for the flywheel, cylinders and every else involved is just silly. My car has since been standing in their workshop for 7 days while they 'had to take out the clutch and send photos to Nissan SA to assess the situation'. That is 7 days without even getting an answer on whether or not they will get it replaced, let alone starting the actual job. I have asked around and not even 4x4 bakkies have clutches that are that expensive to replace. My car does not even have a tow bar fitted, meaning its never pulled a caravan or trailer in its life, so to have the clutch fail at 82,000 km, is not normal. I'm now getting desperate and the friendly patience that I've shown until now, have run out.