I can only speculate. In general, you can expect things to cost more on an island, but the South Caicos rate is more than double Hawaii's (which averaged 21.1 cents/kwh in the commercial sector). It's expensive to import all the diesel used in the South Caicos power plant, so that translates into a higher cost of electricity. The bill actually lists a fuel surcharge to cover the cost of the diesel - it makes up about 40% of the total expense. More than that, however, I believe the high cost has a lot to do with the fact that only one power company operates here - it's a monopoly. I'd be willing to bet that somebody with an entrepreneurial spirit and investment capital greater than my own could do quite well here.
Video of Exhaust
More importantly, however, this island has enormous potential when it comes to clean energy generation. The sun is reliably intense and wind is strong and consistent. The fact that nobody (especially the School for Field Studies) is currently taking advantage of this is pretty unbelievable. I've heard that it's been looked into before and that there was even some sort of resistance put up by the power company, but I plan to re-open the issue. At the very least, SFS should be generating a portion of its energy through clean alternatives.
If anybody out there reading this knows about setting up solar or wind generators, please get in contact with me, especially if you work for a company that does installations.