Sounds right, here is the link

http://taxistmaarten.com/wp-content/uploads/Rate_Sheet.pdf

Island is set up in zones, Orient to Airport is zone 11 to zone 1, $30 for 2, $5 per extra person, charge for extra luggage
Rates change at night, so if you paid more durirng the day than $30 and you made no stops with one bag each, then you probably paid too much, but if you did this at night and or made stops, then it would have been more

J&B