2080ti to 3090. Can now use 120hz mode on my tv. Couldn't if I didn't. Therefore it's upto a 100% improvement in gsync for me and therefore I don't think I can put a price on that as I was buying for HDMI 2.1 not for extra performance.
Precisely this for me. 2080ti = stuck on 60hz, 3090 = 120hz. Therefore it's a massive improvement.
regardless of refresh rate, the framerate is also 40-70% higher depending on the game so thats nice