The only way this works is you make your products obviously better in terms of price/performance in the segments you compete in. You've sacrificed the effect of a halo tier product on mindshare to your competitor, so your value proposition has to completely undermine nVidia.
However, nVidia has a very big war chests. They could give the 50xx cards away for free and not really care, as long as it got rid of the opposition.
I personally think this is a suicidal strategy.