Think of it this way (not the real numbers of course):
Civ A has 4 cities, with an upkeep cost of 4 gold/turn (1 gold per city)
Civ B has 8 cities, with an upkeep cost of 16 gold/turn (2 gold per city, since each additional city increases upkeep cost for all cities)
Now if inflation is at zero percent Civ A pays 12 gold less. If inflation is at 100%
Civ A pays 24 gold less than Civ B. Clearly higher inflation is worse for the bigger civ.
This somewhat counteracts the higher late-game potential of a larger empire (more cottages worked etc).
I thought intuitively that doubling costs for both small and large civs should keep the same ratio. I was wrong, but it's quite tricky.
Inflation hits the civs that have a large portion of their budget allocated to upkeep. So a small civ that pays 20% of their total commerce in upkeep will be hit harder than a large civ that pays 10% of total commerce.
As far as I recall, in standard civ upkeep costs tend to be dominated by city and civic upkeep, so larger civs tend to be hit harder.
In Fall from Heaven, there are more ways to mitigate city and civic upkeep and armies tend to be larger. Thus the difference between large and small civs is less.
Speaking of army costs, small civs need proportionately larger armies. The garrisons can be roughly the same size, but a small civ has more border cities and the requirements for an offensive force is about the same. A large civ can also produce units faster and so needs a smaller buffer.
Short version; size is only part of what makes inflation hit harder.
In any case, Civilization IV inflation has very little to do with real world inflation.
carriers DO cost more than warriors
No. A warrior has the exact same upkeep cost as a carrier (not considering inflation). Granted a carrier is quite useless without some fighters, but say a battleship or a tank division.
There is a slight difference in production cost. Warriors are clearly more expensive. When they are relevant, warriors cost about 10ish city-turns. A carrier costs about 4 city-turns. And the carrier will probably be more experienced too.
I'm a bit unsure about the exact

costs, but I think my point comes across.