This report by the American Public Transportation Assocation, Washington DC-based nonprofit advocacy group, ranks cities in the US by the potential savings a household could have annually in taking public transit versus driving.
Seattle is not exactly known for its stellar record on public transportation effectiveness, but surprise! We are in the top 5! Now if they could only bring the light rail to the UW someday during our lifetime, that would be nice.
If you are a public transportation rider in the city of Seattle, you save an average of $11,350 per year or $946 per month. That's like having a second apartment!
The economy being the way it is, it surprises me that so much of our urban development is still dependent on and dominated by the need to drive absolutely everywhere. Public transit is an expensive investment, to be sure, but it's one that pays back in the end by freeing up consumer incomes for more valuable investments than pumping gas (from third-world tyrants).
Check it out, and see where your city lands on the list!