I doubt race results had much influence on the price point for the D812. Race results increase the number of units sold and Hot Bodies showing at 2012 IFMAR Worlds Buggy Championship Racewill make it a popular choice.

The increase in price for the D812 is in large part due to the upgraded parts. Much like the D8 Hara had an increase in price over the standard D8. Some of the upgrades include -

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Monocoque style suspension arms (similiar to HPI Apache)for strength, stiffness, and ease of cleaning
HB Big Bore long stroke threaded aluminum shocks long suspension travel (longer than Hara rear shocks)
Race-optimized steering
Lightweight drivetrain gears have less rotational mass for quicker acceleration (changed to straight cut gears from spirial cut)
Lightweight aluminum axles
Graphite steering knuckle arms
CVD boots to retain grease in axles and keep dirt out
Adjustable hinge pin heights, kickup, and anti-squat angle (not possible on Hara withoutafter market parts)
Adjustable rear toe-in (inboard and outboard)
Integrated steel skid plate in chassis to extend chassis life</p></font>For Joe Average, the D8 Hara would be sufficient. But there are always those to want top drawer, so there's the D812. After 6 months or so, the price will drop on the D812 and make itan even better value.