Is it cheaper to take a ferry?

Only for very short distances like St. Kitts to Nevis. For most island hops, the ferry is often more expensive and significantly slower than flying.

Why are flights within the Caribbean so expensive?

High fuel taxes, government landing fees, and a lack of competition on specific routes keep prices high. Booking in advance and using regional-only carriers is the only way to mitigate this.

Booking Inter-Caribbean Flights Without Overpaying

Avoid regional airline websites, which often show inflated 'tourist' pricing, and book via local consolidators or multi-leg flight aggregators. Always search using a VPN set to the local country of origin or use regional carriers like interCaribbean Airways or Caribbean Airlines during their specific Tuesday flash sales.

Use a region-specific search engine. Avoid major US-based sites like Expedia for short hops. Use Skyscanner or Momondo, but set your 'Point of Sale' (POS) to the country you are departing from. This often reveals lower local fares not displayed to North American IP addresses.
Book individual legs separately. Don't search for 'Miami to Barbados to St. Lucia' as one ticket. Book the long-haul flight into a major hub (like Barbados or Trinidad), then book the regional 'puddle jumper' flight separately. This prevents 'interline premium' surcharges.
Monitor regional flash sales. Sign up for the email newsletters of Caribbean Airlines, interCaribbean Airways, and LIAT 2020. They run 24-hour flash sales on Tuesdays and Wednesdays that can drop ticket prices by 40%.
Use local currencies. If the airline website allows it, pay in the local currency (e.g., ECD or TTD) rather than USD. Use a credit card with no foreign transaction fees to avoid the markup your home bank would otherwise apply.

Is it cheaper to take a ferry?: Only for very short distances like St. Kitts to Nevis. For most island hops, the ferry is often more expensive and significantly slower than flying.
Why are flights within the Caribbean so expensive?: High fuel taxes, government landing fees, and a lack of competition on specific routes keep prices high. Booking in advance and using regional-only carriers is the only way to mitigate this.