Refineries will NOT give the extra 6d if built in a grain province.
There are no breweries in the game, only refineries. The screen you saw must be a bad translation.
Refineries will not be a 100 year payback. Their benefits are large and fast no matter where you put them:
(a) Base 6d/year added to income (12d if you put them in the suitable wine/sugar provinces)
(b) 5d/month (60d total/yr) added directly to trade research until you max out at level 10.
(c) +1% to your trade income (adds to the modifier for trade tech, so you multiply once, not twice, and can go over 100%, e.g. 100d base income/month * 101% for trade tech 10 and 1 refinery)
(d) +2% population growth rate -- since population size modifies all of a provinces production and taxation numbers, growth is a very good thing.
(e) -1% revolt rate -- since revolts are annoying and resource-wasting, this is another nice benefit.
Since your first manufactories usually cost around 600-700d, even if you put it in a grain province, you'll be making back your investment in about 10 years (600d of trade research and 60d of general income) without factoring in any of the other effects.
In a large world-conquest type of game, just that 1% trade bonus can be ridiculous. As of 1698 in my current Spanish IGC, I have around 30 each of refineries and goods manufactories (which add to production income) Note that almost all of them were built in a single enormous purchase since the cost to build the next manufactory doesn't go up until the ones on order are completed. Since my base production and trade were each around 550/month for a total of around 1100/month, just the 1% added on for each manufactory gives me an extra 330/month (30% * 1100d)! :wacko:
Of course, you have to be careful where you put them. In case you haven't noticed, manufactories are very easily lost during looting -- enemy or rebel action in the province can be very, very expensive...
