At $2 million a mile it will certainly take loads of cash to get enough sidewalks in the greater Seattle area. This article talks about the problems in getting sidewalks in place in the area.
Forty percent of Seattle streets lack full sidewalks on both sides of the road — totaling 650 miles, the city estimates — but installing them is a staggering expense of about $2 million per mile. It’s not just the cost of the pavement: When a curb is built, it changes the flow of surface water, triggering legal requirements for drainage systems, which in turn can involve buying adjacent property. Many cities can build them only as part of a major street-paving project.
It is disappointing and frustrating to see just how far we need to go to make our cities more pedestrian friendly.