[_ptgt]

The expense-to-marginal-population curve shouldn't even be linear--it should be logarithmic. As a city grows, you would expect it to get better at accommodating population increases (by reforming regulation and from investment flowing into local infrastructure projects and making the building process more efficient, as well as workers gaining experience in building the projects).

[jwilliams]

Assuming all other variables stay the same -- with such a large revenue increase you'd assume some would be changing substantially.