Good assumption Clover! The secret is out, the developers, as you say, do it, to make money.
After assisting in the development of a few projects here in Belize, the profits may not be as large as many may perceive.
It costs about the same amount of money to ship materials/supplies from the Port of Belize to San Pedro as it does from Port Everglades to the Port of Belize. Then of course the GOB import tariffs, everyone's favorite on top of the LANDED cost (not FOB).
Then throw in the constant variables (great phrase) of running out of raw materials, back-ups at the port, transportation, weather, etc. There is no Home Depot here.
Just a little clarification on your broad generalization.
Our neighbors here may only make squat (in your eyes), but they make it go a long way here in Paradise (happy people), so give em' a break on the bridge and get em' a cold one when you do run into them.