Why is fertilizer formulated without the necessary Ca, Mg

[Steve]

Why are Chem-Gro and similar products formulated without the necessary Ca, Mg, and SO4 forcing the grower to fiddle around with CaNO3 and MgSO4?

Can't they just include this stuff in the mix?

Where do the hobby places get off charging $30 a gallon for nutrient concentrate when you can buy the same salts in 50 pound bags at prices that allow you to mix nutrient concentrate for less than a buck a gallon? Everyone has to make money but charging $30 for $.50 worth of chemicals is pretty greedy.

Steve