I doubt that anyone in Napa is making the exact same wine under different labels. Probably not in Sonoma either, or Bordeaux, or anywhere that you can sell the fruit based on a vineyard. There are multiple brands involved - the region, the vineyard, the winemaker, and each one will be worth something in the final product.
However, I once imported the exact same wine under different labels. Same bottling line, etc., but one guy wanted a house label, one guy wanted a different label for restaurants, and we liked the original. And I know of a few French wines that were exactly the same wine, as I knew the winemaker, and she had about four labels with the same fruit from her vineyards. Neither of these were big producers, but they needed to get into the market somehow, and just like P&G, they were looking to maximize shelf space. And in a few stores, the wines were next to each other on the shelves.
There was no fraud intended, and the wines were priced roughly the same, except that as usual, a restaurant marked them up more than a retailer. They even ticked the woke boxes - organic, minimal intervention, etc.
There’s nothing particularly wrong with that, and no, the wines were NOT going for over $100, much less $300. But they were good, fairly priced at whatever the label happened to be, and they were honestly made from specific vineyards, not a bunch of random grapes from all over that were then acidified, chaptalized, etc.
Beckstoffer is smart. He’s made his grapes a brand. He’ll charge whatever he can get, and he’ll accept a few squeals as long as the wine keeps selling. His costs for labor and fuel will have something to do with it and those have increased, but he wants a premium for his fruit and so far, has obtained it. That’s going to work its way through the entire chain. And in the case of Myriad, there’s not really much of a retail chain as Mike is selling DTC. So the prices increase for him may well reflect his cost increases, although I don’t know.
If it is important to someone to have Beckstoffer fruit made by winemaker X, then the price will continue to go up until it no longer sells. But I don’t see that happening in the near future.