Economists ask "How do consumers spend their money?", attributing value to goods and services that people pay for.
Also useful to ask "How do people spend their time?" Facebook is valuable in part because 1 in 7 people have decided it's worth some time each day.
What does this mean for cities? One way to be valuable is to be the cafe that sells lots of coffee. Another way is to be the cafe that people come to and stay at all day. One way to measure your bus system is by the number of fares, but another way is to measure bus trips as a percent of total trips. And when building a new high rise, consider the medium income apartments where people will live year-round compared to the most expensive where the owner may just parachute in for a weekend before heading back to their second (or third, fourth, fifth) home.