Exception: both the Bronze and Colonial age GBs can be marginal – check if you really need them for your type of game. If faced with a choice, you should normally build the highest level GB for which you can afford the space and goods construction costs. To summarize though, GBs are nearly always worthwhile building, and GBs of later ages tend to be a BIT better than those of earlier ages, to offset their significantly higher costs. (Reality will be different of course, but it is a useful gauge/estimate). For the purposes of the latter issue, I made a table where I estimated the output value of GBs in the Early, High and Late Middle Ages, with an assumed standard set of houses and supply production buildings. Further complications are that each GB has different combinations of benefits, and some benefits are worth more in different ages (or when boosting better buildings). However, it uses less than half as much space (4×4=16 vs 6×6=36 squares). The Lighthouse, for example, produces 12% less goods than St Marks. Likewise, the space needed is also a big factor.

So is the Deal Castle 267 times better than the Tower? Probably not). Building the Deal Castle though, requires Colonial Age goods that would require 800,000 each in supplies and coins to produce. (A Tower of Babel, for example, costs the equivalent of 3000 coins and 3000 supplies to produce the 150 Bronze Age goods needed.

In part, this is because the initial resource costs of GBs go up significantly – by nearly a factor of 3 for each age. It’s difficult to figure out exactly how much though, and whether the difference is fair or not. On reviewing their benefits, it is clear that some ARE better than others. In effect, they are like large Premium buildings (often much better!), which makes sense given that many were at least partially bought with diamonds, and/or require a LOT of investment to complete. Great Buildings are definitely better and more interesting than regular buildings. Forge of Empires Great Buildings Values Analysis by davidb3

Forge of empires deal castle size