For me it isn't. I have seen bigger rewards around these levels. Check here.And those amounts are still not profitable?
I mean a merchant carrying such a load shouldnt pay to much now should he... Else he is paying you more then his cargo is actually worth
I think that doing Escort Quests from Sao Jorge to Cuba, Eleuthera, or even Cayman, should have a reward about 10,000 gold or more. From islands that are near each other I can understand the low rewards.