Also big brands usually deliver on consistency. Making the same (or very similar) wine year from year on the order or hundreds of thousands of bottles ... yeah, that takes some skill, and favorable location doesn't hurt either :) For example see the big wineries in New Zealand.
But usually if you want something that's exceptional you have to spend a lot on throwing away the unexceptional parts. Not every year will be good, and even if the weather was good there's still no guarantee the wine will be amazing. Yet the costs are there. That's why there's a very hefty premium on brands that only deliver the top-top-top quality. (Obviously they sell the grapes/wine that did not make it under a different brand, but sssh.)
> I assume the big brands get part of the way there by mixing old and new wine, though.
I don't think they can - wine is usually sold by vintage year. "Origin" is usually weaker (e.g., 50% of grapes must be from the declared origin) and my understanding is that is where you can "adjust" year-to-year.
Not mixing between years, but you can mix between different vineyards of the same year. As long as the wine comes from the same region you can keep the branding. There are plenty of contract vineyards that sell to different wineries to enable these mixes.
But usually if you want something that's exceptional you have to spend a lot on throwing away the unexceptional parts. Not every year will be good, and even if the weather was good there's still no guarantee the wine will be amazing. Yet the costs are there. That's why there's a very hefty premium on brands that only deliver the top-top-top quality. (Obviously they sell the grapes/wine that did not make it under a different brand, but sssh.)