There's a fairly low ceiling in terms of walkability within cities though. Once you exceed a certain distance, no amount of walkability is going to convince people to walk, and rent/housing prices within the walking distance tend to be much higher than those outside, thus exacerbating the issue of public transportation.
If you're able to walk for 95% of your needs, public transit, taxis, uber and zipcars solve the other 5%.
If you're only able to walk for 5% of your needs, public transit isn't going to help you much.
Rent/Housing does indeed cost more in walk-able areas. That's a great signal telling us that there's a lot of demand for walk-able neighborhoods, and urban planning should allow a lot more of them.
