Minimum cost (in US $) to hand harvest one ton of wine grapes in the Central Valley of California. According to a recent study conducted by the University of California at Davis, 5 to 6 agricultural workers are needed to pick one ton of grapes an hour in that large flat agricultural region. The average total cost for picking a 7-ton vineyard would be between $560 to $700 per acre. In contrast, machine harvesting would cost between $275 to $350 per acre. The cost of harvesting elsewhere in California is much higher than in the Central Valley.