When your factory or RGO produces more than what is sold, it would be nice to have the option to buy it for your stockpiles from your factory at a reduce price or perhaps at cost.
If that isn't possible, perhaps the factory should have an output inventory that could accumulate (up to a point). I think I like the first option better though.
If that isn't possible, perhaps the factory should have an output inventory that could accumulate (up to a point). I think I like the first option better though.