The ride actually costs $2 from BWI (it's $1.15
only with a rail-to-bus transfer which you need to get
on the Metrorail system itself). Also note that a
similar bus (the 5A) runs from Dulles right into the
District, so both airports have much better accessibility
than they used to.
Quoted:
For those of
you planning to fly to DC for ACF Nationals or
PACE
NSC, be aware that Washington's Metro authority
has just
introduced a $1.15 shuttle from
Baltimore-Washington
International (BWI) to the Greenbelt stop of
Metrorail. BWI is,
generally, considerably cheaper than
National or Dulles, so in
exhange for about 1-1 1/2
hours on mass transit, you could save
upwards of
$50/person.