Why are Cabs from Dulles to DC so expensive?

Photo by PoPville flickr user Jen Tuohy

A reader asks:

“I’m living out of the US at the moment, and was planning a trip back to Washington. I noticed on this Dulles Airport page with “Estimated Taxi Fares” (of course, pretty much locked in with Washington Flyer), that the estimated cost from Dulles Airport to Rosslyn is $28.00 for 25 Miles. However, cross the bridge into DC (26-28 Miles) and the cost for Dulles-DC is suddenly estimated at $60.00-$64.00. Same thing for Dulles to Pentagon City (26 Miles, estimated cost is suddenly $64.00).
See for yourself.

I was just a bit astounded by this…. It’s a bit over the top.

I’m a bit flummoxed… is there some sort of tax or surcharge to these places? Just a truly wild disparity.”