Octavia RS DPF issues

I've been having power delivery issues with my 2009 Skoda RS diesel DSG over the course of this year and have had the exhaust pressure sensor, throttle actuating valve, and turbo waste gate valve actuator replaced to try and fix the problem. After spending about $2000 I've now been told that the Diesel Particulate Filter is clogged with ash and needs to replaced, and the part alone will cost $4000!! This is a 'consumable' item under the terms of the warranty, but I'm countering that the exhaust pressure sensor being faulty has meant that there hasn't been any warning of impending issues there, meaning no re-gen. I drive regular freeway trips and service the car religiously. It's done only 65,000 km and I don't feel that a $4000 part should fail within five years and nominal km. I've had the car at the dealer for five weeks now and am still none the wiser as to whether they'll come to the party with a goodwill claim on the part cost. Any idea how I can get a resolution?