The wine business is at its heart a business, and nothing can happen if you can’t make a profit. For vineyard owners, this means the selling price of their grapes (either as fruit to wineries or in the form of finished wines) must be high enough to cover the costs of the season — pruning, labor, new grapevines, soil amendments, fertilizers, and the like. In 2015, UC Davis estimated that it costs about $4800 per acre to farm a vineyard in California’s Sierra Foothills, a rural and inexpensive growing area compared to more prestigious regions like Napa and Sonoma. In the foothills example, UC Davis estimated a sale price of $1,300 per ton for the grapes, meaning a vineyard needs to yield about 3.7 tons per acre to break even. Most vineyards average four to six tons per acre, making it easy to see that margins are slim in the best of scenarios.
http://vinepair.com/articles/the-farm-to-table-movement-is-wrong-mechanical-harvesting-isnt-bad/