Well, I don't get the $43.75 *each* to spend on taxi and drinks while you wait for your flights. You'll already have committed $40 approx on your taxis from the Inter to the Muni and back again. So you are down to $47.50 for drinks. Sure that sounds like an OK deal. You need to decide what means more to you, time or money. For my money, I'd rather have the time on Ambergris Caye than saving it by driving around in a rickety old cab of some sort instead of having my feet in the sand while I quaff my first libation. I agree having a drink or two with Jet at the Belize International Airport can be fun, but given my druthers, I'd druther be having it at Fidos or Cholos.
And when it is time to go home, I believe that you are going to want to be able to squeeze every last hour you can on the island, rather than leaving the island early so that you can ride in a taxi from the Muni to the International.