@Tom Fidrychit really depends on where the vineyard is, what you bought it for and how the wholesale grape & wine market is doing. Not much different than residential real estate!
If you grow a varietal that is in demand and it’s in a more prestigious area, then you will make more money. If you grow something over-planted in a less desirable area your grapes may go unsold some years. There a cyclical shortages to planting booms to surpluses and around and round it goes.
Also, to be clear, you have to separate the vineyard from the winery. The vineyard is a farm, the winery makes the wine, and many do not own vineyards. Most wineries have trouble being profitable beyond just being a job for the owner. It’s beyond over saturated, so marketing is your real challenge. There are also many wineries who farm but also buy bulk grapes or already made wine from wholesale markets. This is often a smart move from a financial startup POV, especially in a glut market. In tight grape markets, your COGS is cheaper if you farm your own grapes.
The challenge for the industry as a whole going forward is that the wine industry has not done a good job of courting younger generations into the entry level, let alone getting them to spend $25-100+ a bottle.