Google Sharon Zukin. She wrote a book on loft living and describes the decline-rejuvination cycles in cities. According to her poor artists are the reason for those million dollar valuations.

Cycle goes something like this. Factories in parts of the city shut down after it get cheaper to run them outside. Those spaces lay empty, rents drop, decay begins. Poor Artists move in. Area starts getting interesting. Yuppies move in cuz of the 'cool' factor. Property developers notice. They start buying everything up. Rents jump. Artists get kicked out. And you end up with boring rich people living in a formally cool area.