This is not true. Farming has always relied on exploited labor in some form. Once easily exploited labor disappears with no machinery to replace them, so too does an agricultural industry. Lots of developed European nations are facing this exact problem.

Paying people proper wages will either cause food to get massively more expensive, or will migrate production to crops that are more readily harvested by machines. So grains will still be dirt cheap, but meat and vegetables will be very expensive.