Lower land costs, lower wages, governmental economic incentives such as subsidies and tax breaks, the same things that prompt any corporation to move operations.
Farmers here use illegal immigrants so the wages are a wash.
These particular farms already have land, why buy more. Especially
considering that the movement of equipment would be an added cost on top of a wash. That ain't it either.
Subsidies are available and plentiful here, so that's a wash as well.
What other reasons would an organic farm decide to massively relocate to
Mexico (while keeping their farm open stateside)?