We hear a lot about "rates of production" for various cities, but never is it explicitely mentioned that you actually need to pay for them. And this would normally be enough for me to assume that you don't need to pay, but I've never played a strategy game where producing units didn't cost something. Not to mention that it is heavily implied sometimes. Like, say, in this text update
http://www.erfworld.com/summer-update-2 ... ration.png
Vanna had been the perfect solution. Having a Turnamancer reduced the production of an heir by twenty turns, and with funds coming in from Transylvito, Vanna was able to boost Otoh and Kibo's production drastically
That implies that they wouldn't be able to produce at a higher rate without extra income. Therefore, income is necessary for production. Of course, if this was the case, you'd think it would have been mentioned explicitely at some point. Though I may just have missed the bit where they mentioned it explicitely. So does anyone know?