I think the super increase in production of workshops is Inno's way of making up for no longer giving free expansions. I have 4 magic workshops and when used with PoP spells they produce more supplies than I can use. I typically have a 125% culture bonus, which helps, but I'd still have too many supplies without it. I'd just have to use more PoP spells, but I have 1600 of them so I'm not in immediate danger of running out.