If they can make food cheaper, what pressure is there to sell their product at a lower price? The economic answer is that a competitor will do it first to get a larger marketshare, but the pratical answer is nothing will force them. If the regulatory and capital cost to enter the market are high, then a competitor isn't likely to appear and the existing players can continue functioning in a quasi-cartel.

Taking this to its logical end, the owners of said farms will get richer as the general population earns less on average (due to their labour no longer being needed).