I dont believe that at all. For every 2080ti, a dozen or more 2060s will easily be sold. If even as a rough representation, the
Steam Hardware Survey bears that out (ie, 1060 vs 1080ti owners). The 2080ti is almost double the price of the 1080ti, which will should diminish its sales even further compared to mainstream/mid-range cards. The 2080ti is more of a statement product than real money earner. The 2060 sales volume will generate more profit easily.
Secondly, $300 manufacture cost (if true) of 2080ti does not stop at the cost of the HW parts only, but extends to packaging, marketing, distribution and most of all, R&D expenses. All that has to be factored in. I would think all that can easily put the card costs over the $500 level.
Finally, RTX cards are a different beast altogether from any of Nvidias previous gens. Nvidia is staking their (gaming business) future on the success and widespread adoption of ray tracing in PC gaming. High prices will only hinder that for them and game developers will care less about RT if only a tiny percentage of GPU owners can use it.