Back in late v38 I ran several games with more or less insane increases to city maintenance, getting close to the point where you could go bankrupt on on a single city or not really afford to expand at all in late prehistoric/early ancient era. What I found was that as ages go past and you get into classical and medieval era those maintenance cost still ended up getting small compared to your income.
The conclusion of that was that with the scale of golf income going on it did not seem possible to handle the "too much gold" from the angle of city maintenance. Considering that the old inflation, with its various problems have been more or less sterilised, then we cannot even use that to kind of deal with the problem.
In response to this I have come up with two suggestions for handling the "too much gold" problem:
1) Change the scaling on city maintenance. Currently costs for a new city scale linearly with number of cities and distance to capital. We could change this to say quadratic scaling, which would increase the range where adding more cities would still be a significant cost, which in turn would limit very wide empires and give value to gold income.
2) Reduce the scaling of global brutto income to sub-linear. This would work somewhat similar to wastage on food surplus, in that it would provide diminishing returns on further investment. The big difference is that it would be applied globally and on income instead of profit. This would have an effect similar to increasing maintenance costs, but affect the general balance differently, in that other expenses would also be affected, and that surplus gold would grow slower. The phenomenon behind this would mainly be corruption and inflation. Here is how I imagine that the formular would look: G = g/S, where g is the brutto global income and G is the effective global income (which is then substracted from expenses). S= [1 +a*log(g)]*[g/c]^b, where a, b and c are variables that can be chosen and possibly modified by civics, wonders, and difficulty. All of this would naturally need some clamping to prevent problems at low g. I would suggest starting values around a=1, b=0,5, and c=1000, as this would create a noticeable diminishing return early that still allows for reasonable scaling to a few cities, and later on the huge income would have a square root applied to it, which should keep maintenance and such relevant into the middle eras. Note that the reduction in efficiency as you earn more money will provide a similar effect to the increased inflation when you rush buy units or buildings, from the simple fact that it was that much harder to produce that last bit of gold. Thematically the logarithmic turn comes from corruption/beuocracy, based on the idea that as your civ becomes larger there are more and more layers of administration that can take a piece of the pie, and the amount of layers money would have to pass through is generally logarithmic. The geometric term would then thematically be based on inflation and the commonality of goods, where the more you can get of each thing the less they become worth. Thematically early empires had a lot of trouble with corruption and beuocracy, while inflation and commonality of goods is more influential later in history, which reflects well in how their effects are staggered.
There are several pros and cons to these tools, and I invite you to discuss them and see whether any of them or perhaps some combination would be useful for the current or future gold balance.
The conclusion of that was that with the scale of golf income going on it did not seem possible to handle the "too much gold" from the angle of city maintenance. Considering that the old inflation, with its various problems have been more or less sterilised, then we cannot even use that to kind of deal with the problem.
In response to this I have come up with two suggestions for handling the "too much gold" problem:
1) Change the scaling on city maintenance. Currently costs for a new city scale linearly with number of cities and distance to capital. We could change this to say quadratic scaling, which would increase the range where adding more cities would still be a significant cost, which in turn would limit very wide empires and give value to gold income.
2) Reduce the scaling of global brutto income to sub-linear. This would work somewhat similar to wastage on food surplus, in that it would provide diminishing returns on further investment. The big difference is that it would be applied globally and on income instead of profit. This would have an effect similar to increasing maintenance costs, but affect the general balance differently, in that other expenses would also be affected, and that surplus gold would grow slower. The phenomenon behind this would mainly be corruption and inflation. Here is how I imagine that the formular would look: G = g/S, where g is the brutto global income and G is the effective global income (which is then substracted from expenses). S= [1 +a*log(g)]*[g/c]^b, where a, b and c are variables that can be chosen and possibly modified by civics, wonders, and difficulty. All of this would naturally need some clamping to prevent problems at low g. I would suggest starting values around a=1, b=0,5, and c=1000, as this would create a noticeable diminishing return early that still allows for reasonable scaling to a few cities, and later on the huge income would have a square root applied to it, which should keep maintenance and such relevant into the middle eras. Note that the reduction in efficiency as you earn more money will provide a similar effect to the increased inflation when you rush buy units or buildings, from the simple fact that it was that much harder to produce that last bit of gold. Thematically the logarithmic turn comes from corruption/beuocracy, based on the idea that as your civ becomes larger there are more and more layers of administration that can take a piece of the pie, and the amount of layers money would have to pass through is generally logarithmic. The geometric term would then thematically be based on inflation and the commonality of goods, where the more you can get of each thing the less they become worth. Thematically early empires had a lot of trouble with corruption and beuocracy, while inflation and commonality of goods is more influential later in history, which reflects well in how their effects are staggered.
There are several pros and cons to these tools, and I invite you to discuss them and see whether any of them or perhaps some combination would be useful for the current or future gold balance.
Can't have that now can we!) Instead it's a slow process of trial and error testing to see how it plays out. Auto games can not give this depth of game play interaction or overall feel. Only truly played games can.
The word leveraging, what every player does with his particular game flow, does threw you for a loop. Sometimes you dive way too deep when it's only shallow water. 
penalty through civics that goes down throughout the game until the mid modern era where it hits -0%
