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?
I have learnt several factors about mining and done some research about it. I never thought of mining since the electrical costs are so high.
The halving would at most halve the earnings and would probably have an impact on the prices. If you didn't know, most mining farms started in around 2014 and they have made lots of profits. There are still some scrap value for the ASICs that are obsolete too. A documentary about a mining farm in China:https://youtu.be/K8kua5B5K3I.