so like you said, we are only a couple of weeks into this, so this is just a guess... i think the financial aid department did a pretty good job on estimating costs, but I can give you some more specifics...
I am one of 22 students in my class, I live 10 minutes (walking) from school in Camps, and I share a 2 bedroom apartment/house with my roomate/boyfriend for $1100/mo ($550 each). Most people don't have roomates, and probably pay more. We haven't got our electricity bill yet but we only have two small airconditioners in the bedrooms that we only run at night, along with some lights and fans... we don't anticipate it will be too much over $150 US. Water is included in our rent, along with yard maintenance, but we did have to hook up the cable and internet which is about $100 US/mo. Then we also received digitel cell prepaid phones upon arrival.... we just use them to talk to friends at school or else it's too expensive to call home. If you spend $10 EC, you can talk for a few weeks. We decided to get yahoo voice and set up a number on our computer with an area code from Ohio (where we are from)... the incoming line with voicemail is $30/year and you buy credit for outgoing calls ( 1 cent per minute to call the US). Food can be pretty expensive here. They tend to import EVERYTHING, even fruits and vegetables that seem like they could be grown here (normally have a "USA" sticker). I would say between the two of us, we spend about... $400 EC/ week on groceries, plus a few snacks from the bookstore here and there. Transportation isn't too bad when you live as close as we do. We walk to school and anytime we want to go downtown (Basseterre), we hope on a "bus" (a van with a HA or H license plate) for $2 EC one way (less than $1US). Sometimes you need a taxi, which can be a little pricey, but no more than it is in the US. When we get groceries, we take the bus there, or walk, and take a taxi home for somewhere between $10 and $20 US. The beach part of the island, Frigate Bay, is a $20 US taxi ride away (tip included), and the buses will not take you there, so if you want to go to a beach, it will cost you, unless you hitch a ride or have a car. If you want to buy a car, there are lots of students selling cars for around 3-4K US, plus you have to get insurance and your license (~$100EC). You can also rent for about $300US/mo, or share a care with someone. So far, we haven't had much time to do anything "entertaining" that would cost money besides a few dinners here and there. Like I said, I think Allysa and Calvin (the financial aid team in NY) have done a really good job of making sure we have enough money to make it through the semester... the hardest part was the upfront expenses of plane tickets, laptops, vaccines, etc.
I hope that answers your question...