In New York City, the value of a taxi medallion, simply a license to operate a taxi cab, is $477,000. That is an amazing sum, but certainly understandable by the law of supply and demand. The demand for taxis is always high in NYC, and with Mayor Bloomberg's proposal to dramatically increase the tax/tolls to enter Manhattan via car, it is likely to grow even higher. As for the supply, NYC limits the number of licenses available, so it does not take a genius to see why the prices of medallions are outpacing other investments in New York.
Here in St. Louis we have the Metropolitan Taxicab Commission. While I don't like all the regulations it has for cabs (the dress code for drivers is particulaly stupid), it is certainly preferable to the system in place before its establishment in 2003. Before then, the county and city each regulated their own cabs and prevented crossover, so a county cab could pick someone up in the county and take them to the city, but then was not allowed to pick up a fare in the city. So the current system is at least a little better.
Unlike NYC, St. Louis does not, as far as I can tell, set a numerical limit on the number of licensed taxis. This is a good thing from a free-market perspective, but the commission does have broad powers to deny new licenses if it feels the market is currently being met with existing licenses. As the commission is largely composed of people with direct involvement in the taxi industry, the potential for limiting the number of competitors by limiting new licenses is certainly there.
The cost for a taxi license in St. Louis is $55 per year. Judging by how hard it is to get a cab in St. Louis, I'd say there is not exactly a line forming (pun intended) to drive that value up. In NYC it is $477,000 for a medallion. That is an 867,172-percent greater value. Based on my perceptions of the cab industries in both towns, I'd say that sounds about right.