I think it's almost tautologically true that higher density requires (for example) less road, and less road is cheaper than more road. So that would just mean t

I think it's almost tautologically true that higher density requires (for example) less road, and less road is cheaper than more road. So that would just mean the differences you pointed out must be external to this analysis. As a first stab in the dark I'd ask: does Oregon City have any poor people, or old people? If it's a rather new community build as a satellite for Portland's professional class, the demographics may be completely different from that of the state as a whole. Portland may also suffer from its past: maybe they have pension obligations that they didn't build capital for. Or, conversely, Oregon City may be underfunding its future obligations. I also just looked u the numbers to see what the difference is and you are right: Portland Pop: 604,000 Budget: 4,000,000,000 = $6600/person/year Oregon C.Pop: 34,000 Budget: 165,000,000 = $4860/person/year