This $400,000 super-wagon is coming to Australia before the BMW M5 Touring, but for those after an Audi RS6 Avant GT, there's a catch...

Audi has confirmed that just 22 examples of its hardcore RS6 Avant GT wagon are coming to Australia.

The cost? That'll be $399,000 before on-road costs. Absurd, right?

Clearly not too ridiculous for fans, because even though it's nearly $150,000 dearer than a regular RS6 ($251,000), all examples are already spoken for by Audi die-hards.

There are a total of 660 RS6 Avant GTs being built worldwide and Audi Product Planning boss Peter Strudwicke admitted the limited edition wagon was likely to be a collector's item.

“I guess it probably would be given the level of interest. You never know with these things but it’s good a chance as anything," he said.

The exterior appearance is inspired by racing heritage, namely the Audi 90 Quattro IMSA GTO race car from 1989.

Australians only get the choice of two colous: Arkona White or Mythos Black. The dark finish is complemented by more subdued shadow graphics than the white car.

The flared guards house 22-inch Avus inspired alloy wheels wrapped in huge 285/30 Continental Sport Contact 7 tyres.

A carbon bonnet (you can see the weave through the livery) and carbon mirror caps are joined by aggressive bespoke bumpers, a rear diffuser and roof spoiler.

To tidy up the aesthetic further, Audi has deleted the RS6's roof rails.

As standard, the RS6 Avant GT is fitted with manual adjust coilover suspension with tweakable ride height, rebound and compression control.

Buyers can opt for air suspension or adaptive dampers, if they wish. A Quattro Sport rear differential completes the corner carving changes.

Audi's RS division hasn't screwed any more boost into the RS6's 4.0-litre twin-turbo V8 so outputs of 463kW and 850Nm are unchanged compared to the Performance.

It's still faster, thanks to a more dynamic tune of the eight-speed automatic transmission which gets the RS6 GT from 0-100km/h in 3.3 seconds (one tenth faster). The speed limiter is raised to 305km/h, too.

Inside there are body-hugging RS bucket seats, red and copper stitching, red seatbelts, 'Dinamica' interior trim elements, special floor mats, sill trims, different entrance lighting and a numbered plaque on the centre console,

Australian cars benefit from the Sensory Pack, which includes a Bang & Olufsen Advanced stereo, rear window sunshades, a leather-wrapped steering wheel and heated rear outer seats.

The RS6 GT is the swansong for the current RS6 with a new, electric A6 coming as a replacement. BMW's closest rival, the M5 Touring, is soon to launch with a plug-in hybrid V8 powertrain.