This is IMO where I've arrived at too. Some wine really sucks. Some wine is incredible. I've definitely been surprised by some <$20 bottles but in general $50+ wines are not going to have the same flaws that are common in cheaper bottles.
With that said... I've had some terrible bottles of $100+ wine from well regarded wineries.
IMO after $50/bottle, Napa Valley and some French wines take a huge drop in quality. The higher-end wines are trading more on marketing and branding than on the culinary experience.
With that said... I've had some terrible bottles of $100+ wine from well regarded wineries.