I have went shopping with my girlfriend in San Fransisco a few times, and got to thinking about how most of the businesses in the city pay $4,000 to $20,000 per month for rent. In many cases, with a 5 year term.
You can buy a great domain name for that. You can compete in the search results in most markets for that. Monthly rent to buy exposure in one city is recurring. Many online marketing costs and domain costs are not.