Farmers get their inputs much cheaper than I do, especially water. Water is essentially free compared to residential rates at about 100x cheaper.
I dont think water forms a large % of the cost of fresh veg - certainly not relative to logistics and spoilage.
If you factor in wastage and the expensive supply chain logistics for things that spoil quickly it's probably cheaper to grow them closer to the point of use, especially if you can keep down labor costs with automation.
Tastier and more nutritious too.