When I was a Girl Scout I sold them for $2.50...but back then the price of everything was cheaper than it is now...I agree $7.50 is steep, but $3.50 / $4.00 a box is really not that bad. The price of milk has gone up at least $3 since I moved out of my parents house and gas...let's not get started on that...if in 15+ years they have gone up $1-$2 dollars I don't see an issue with the price (as long as they are not $7.50) ;)
Maybe if you want to take the issue up with the GS' maybe write a letter to your local GS counsil?