American Airlines has round-trip flights from New York (EWR) to Saint Kitts (SKB) starting at $315 with a connection. Flights sparse and scattered in October, January, and May. “Regular Economy” is available for +$25 more each-way.
Note: One-ways for $138 are scattered from September to June. See list of example dates.
Note: “Basic Economy” fares do not include a free carry-on bag. Only a small personal item, like a Jansport City Scout backpack is free. Checked bags cost +$25 each-way. Seats are randomly assigned prior to boarding. If you have an AAdvantage credit-card you can avoid bag fees.