You lucky son of a gun! $120 for a flight to Dominican Republic. Ok, granted it is a single flight and not return, but when you are travelling like yourself - wandering and seeing more you will end up - that's great.
We would imagine most of these islands in the Caribbeans would be expensive due to the importing of many produce. We can imagine the islands would have a deficit of many items.
We thought you might have brought the tickets for cheap as it's not the season to go, but from the photos it is sunny and bright!