They are expensive, but, like any product sold from an organization, it's not so much the cookies that you're paying for, but to give to the organization itself. According to the GS website:
"Cookie revenue" helps local councils:
Recruit and train volunteer leaders for each troop/group.
Provide the financial assistance needed to make Girl Scouting available for all girls.
Improve and maintain camp and other activity sites.
Keep event/camp fees for all members to a minimum.
Sponsor special events and projects.
I don't mind giving to something like that, and getting a tasting treat in the process. }(