From Wikipedia: "Trinidad and Tobago is the leading Caribbean producer of oil and gas" They're apparently floating on the stuff and run mostly on natural gas, so I suppose they can set their domestic pricing wherever they want.
One of the reasons diesel is high here in the US is a demand issue, we use lots of it as motor fuel for trucks, trains, equipment etc, but the largest market is home heating fuel, the Northeast as I recall is heavily dependant on it, which skews the price upward. I would think that in the Caribbean they wouldn't need much heat, if any, so diesel is probably plentiful from the refineries there.
Just guessing, YMMV