A few things;
720s OEM pad cost isn't much different than the rest of the sport and super series cars cost. (ultimate series is much higher).
Taxes make importing rotors/pads from Australia fairly expensive (as an example in USA; I ordered surface transform rotors but had to pay $400 for import duty/taxes. I purchased them directly from Surface Transforms in the U.K.
If you have to buy the pads from outside the country (OEM or aftermarket), then you are going to be paying much higher then what we do in the States.
Anyone who has tracked 720s/600LT more than a handful of times, knows that the front pads go out quickly.
You have to consider how much you are going to track in order to determine how much money you are going to pump in with the aftermarket rotors/pads and if it is worth it.
I know many, many 720s/600 LT owners who have gone aftermarket. The most affordable option is the Giro discs and Endless or Cobalt pads. They last a very long time (primarily because the pads are thicker (15 mm vs 10 mm (OEM).
I know 4 people who I regularly track with who went with Essex/AP brake kit (vs about 20 who have gone with giro). Essex/AP is a more expensive option but comes with its own calipers. This kit can be used with 600lt/720s/765. The giro kit is interchangeable between 600 and 720s but not 765.
The market is very thin to re-sell the brake kit. Therefore, most will go with the giro set up as it is the most cost effective and a small cost (relatively speaking) to eat if you just throw them away after selling the car.
If you already went through a set of pads then you already are getting hit with the cost as you will have to eventually replace the OEM set when it comes to selling the car, even if you go aftermarket.
Anyone who has spent any time on these forums would know that the pads/rotors go out fast and should have changed to the aftermarket immediately or after the first couple of track days.