SAM isn't that much performance. Based on the slide AMD showed, SAM plus RAGE is an average of 5.5%, or 6% if you ignore the outliers of DOOM and Forza.15-20% where?They said 18% average with SAM enabled.And SAM working only on ryzen 5000+B550/X570 and add another 5-11% performance.So it will be like 8-10% in wide game test without it.
However this number includes Rage, which AMD has stated is responsible for 1-2% of the performance uplift (source). So SAM on it's own would bring about 4-4.5% on average.
The slide from AMD of the 6800 showed it roughly 15% ahead of the 2080 Ti with SAM, so it would be about 10% without SAM.
So not 15-20% faster, but not $200 more either.
But basically no one agrees with that price though, so that's hardly relevant.NVIDIA doubled the price for 10% higher performance and double the VRAM