> Firstly, walkability only means higher prices if supply is limited.
Isn't it, though?
In fact, not only is it limited, it's also a market on the supply side.
> Secondly, a grocery store needs say 500 potential customers (households) within walking/transit distance.
In consolidated urban areas with medium density occupation, such as city centers in pretty much any relatively large European city, you already have multiple supermarkets at a stone's throw. In some places like Madrid some suburban areas even have multiple supermarkets in the same apartment block. Feel free to do a quick search for "supermarket" in Google Maps and just look around.
Isn't it, though?
In fact, not only is it limited, it's also a market on the supply side.
> Secondly, a grocery store needs say 500 potential customers (households) within walking/transit distance.
In consolidated urban areas with medium density occupation, such as city centers in pretty much any relatively large European city, you already have multiple supermarkets at a stone's throw. In some places like Madrid some suburban areas even have multiple supermarkets in the same apartment block. Feel free to do a quick search for "supermarket" in Google Maps and just look around.