You can't compare industrial farming economics to a local community polyculture farm. It's a completely different game. I would argue the local CSA model is far more sustainable than industrial ag, and this is a clear example.
Industrial Ag requires thousands of acres of subsidized monocrop, big machinery, expensive seed (thanks to Monsanto), expensive fertilizer, transportation, and low-wage farmers and crop pickers to make a profit. It's an industry supported by big ag corporations and (thanks to their lobby efforts) government to maximize profit for the few at the top of the chain. The farmers and crop pickers are the last in line, as far as the revenue stream.
A CSA puts money in the farmers and crop workers first, works within and supports the local community. That's why it works, that's why it's sustainable, and expect to see more of them because the local food movement has legs, not because it's a fad, but because it is rooted in a sustainable design model.