Most mining farms are located in China. China are known to have good climate, low labor cost and low electrical cost. With these factors, their profitability is already quite high. Since big ASIC makers like Bitmain being based in China, they can potentially factor out the high shipping cost with discounts given at high ASIC buying volumes. Most farms have hardware that have already ROIed so they're making pure profits now.
Have you ever looked into mining yourself?
As far as I know these days farming countries are not that rich economically as compared to those who are relying on their industry and inorganic products. Mining might be good in china since china is affordable for every thing including farming as well but bitcoin is much better paid off than farming or mining.