The same basic situation exists in New York City. They're called taxi medallions there, and the small supply and large demand causes them to cost a surprisingly large amount of money. The government even has a convenient graph of the average price over time:

http://www.nyc.gov/html/tlc/downloads/pdf/price_trends_chart...

That shows a cost of 359,000 in 2006. More recent data is even crazier:

http://www.nyc.gov/html/tlc/downloads/pdf/avg_med_price_2013...

According to that, they cost a million dollars apiece these days.