> If I could build a cheap system with around 200GB,
Even if AMD dropped the price to $2000, you could not be able to build a system with one of these cards. You cannot buy these cards at their current 5 digit pricing. The idea that you could buy it if they dropped the price to $2000 is a fantasy, since others would purchase the supply long before you have a chance to purchase one, just like they do now.
AMD is already selling out at the current 5 digit pricing and Nvidia is not affected, since Nvidia is selling millions of cards per year and still cannot meet demand while AMD is selling around 100,000. AMD dropping the price to $2000 would not harm Nvidia in the slightest. It would harm AMD by turning a significant money maker into a loss leader. It would also likely result in Lisa Su being fired.
By the way, the CUDA moat is overrated since people already implement support for alternatives. llama.cpp for example supports at least 3. PyTorch supports alternatives too. None of this harms Nvidia unless Nvidia stops innovating and that is unlikely to happen. A price drop to $2000 would not change this.