Wow! We just returned from AC on 11/27. Our experience was nothing but great!
ALL of the restaurants we visited stated prices in Belize dollars. We never paid more than $20 for dinner, and we ate very well!
We took a taxi from Blue Tang to The Belize Yacht Club, and it was $7 BZ. We confirmed the price BEFORE we left The Blue Tang - ALWAYS do that no matter what country you are in.
Belikins were $1.50-$2.00US no matter where we went. Rum punch was $2.50-$3.00US.
Not sure where you were, but it sure does not sound like anywhere we visited in AC.