Okay neat— the WP page for it mentions it being produced at least in part as a byproduct of steel production: "In the finishing of steel prior to plating or co

Okay neat— the WP page for it mentions it being produced at least in part as a byproduct of steel production: "In the finishing of steel prior to plating or coating, the steel sheet or rod is passed through pickling baths of sulfuric acid. This treatment produces large quantities of iron(II) sulfate as a by-product." https://en.wikipedia.org/wiki/Iron%28II%29_sulfate#Production_and_reactions https://en.wikipedia.org/wiki/Iron%28II%29_sulfate#Productio... So I guess that explains why it's so inexpensive, but of course as with many such things (natural gas from oil production, whey from yogurt/cheese production, etc), once there's a robust market for the "byproduct", it can result in changing the original economics.