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).

Before it gets that far, they build a hierarchy of underlings that oppress the labor force. (See CGP Grey's "the rules for rulers" on YouTube.)

Either that or everyone else gets fed up and violently overthrows them. It could, perhaps, be avoided with higher taxes on the rich, but the rich have the most influence over the tax code.

The government steps in and subsidizes food for those who can't afford it, either by printing money, or using taxes. The end result is robbery from the commons while your four mates who give you kickbacks and a cushy post government gig get richer.