Actually offshore wind is cheaper than diesel. Diesel internal combustion generators is just about the most expensive way to produce electricity, by a long shot.
Not on a small off-grid community. I think you'll find offshore wind farms cost millions, while you can buy a diesel for $1000. Stop making irrelevant comparisons that ignore scale. A diesel generator on the grid is as silly as an offshore wind-farm for a small isolated community. Nobody is replacing diesels with wind, though they might experiment with supplementing it.
My point was that this project is funded by selling power to the grid, and selling it to the island is just a PR point.