There are lots of threads on here on brakes - it will pay you to spend a bit of time looking through some of them to get the picture regarding the Touareg.
First, it seems strange that you've effectively worn your brakes out in 5,000 miles. If this really is the case then first I'd suspect an issue with the calipers sticking and not releasing fully [as long as you've not been riding the brakes!].
Secondly, the discs/rotors on Touaregs are unserviceable after just 1mm of wear on each side of the disc/rotor.
Some people do get two sets of pads to one set of discs/rotors but the norm is for Touareg brakes to last at least 60,000 miles [with some owners clocking up 100K and more!] so usually the discs/rotors are changed along with the pads and the brake wear sensors.
However, the first thing a competent mechanic should do is to inspect the discs/rotors for any cracks and grooves and also measure the remaining thickness of the discs/rotors to ascertain whether or not they will take another set of pads.
Brakes aren't rocket science so do get a second opinion - and quote - if you have a trusted mechanic you can discuss this with.
Note that dealers will often try to get you to renew all four corners at the same time. Whilst this may be the best practice in the workshop, it's not the best practice for your bank account!
The OEM discs/rotors are Brembo and the pads are Pagid if you want to stick with original suppliers.