We have the exact same methods for producing gil but each server has a different max amount of gil it can produce daily directly correlated to the servers population.
For example a server that has 12,000 players generating their max 25k a day will produce 300,000,000 million gil a day, while a small server of 3,500 players at 25k a day will only be able produce 87,500,000 million gil a day at MAX. At max gil generation, smaller servers will never reach numbers like larger servers. Server size directly correlates to how much a server can pump out at MAX gil generation.
It would be illogical to put legacy or high population prices on smaller or medium servers, when it would take nearly x3 more work or even more for those servers. When we do the math, regardless of the server sizes, its the same amount of work required for each server even if it appears 80 million Gil cheaper. The max output gil generation of smaller servers and medium servers would never match those of a fully populated server.