I recently purchased my 9th city. With every other one of my cities I noticed an increase in net revenue per turn of around 20,000 per turn. Before buying my next city, my net income per turn was 188,000. After purchasing my 9th city, Pine Grove, I fully developed it to my 1600/1600 standard. I equipped it to the exact same standard as the other cities with the exception of coal mines instead of iron mines. Upon revisiting the revenue page I found that my revenue per turn only increase by 3,000 per turn. The city is powered and has 5 coal mines, 1 steel mill, 100% commerce. The expenses of the city only totaled 7,500 per turn but should have a gross income of 34,000 per turn according to the formula. I believe this is a bug because I should've seen an increase in profit of 26,000 per turn instead of 3,000 per turn. When I purchased the city I DID NOT build up my military, it stayed the same. The city is 100% powered by a Nuclear power plant and I have plenty of Uranium. I have enough resources to run the steel mills. I am very certain that I've not overlooked anything. Every other city I own I never saw an issue with until my 9th. All of which are powered and built to the same standard.