Mercedes S55 AMG (!) taxi cab (Walnut Creek)

This is a head scratcher.  I saw this on the highway yesterday.  It looks legit.  I called the number and a guy with a cool Eastern European accent picked up.  Da, da, it's a real S55.  A ride from Walnut Creek to Oakland Airport costs around $65 (this is pretty reasonable).  I'm going to use it next week.  My first question when I meet the guy-- How are you not bankrupt from the operating costs?