from Verizon's own site, "pay as you go" talk rate is $1.79/min (Texts = $.50 send/$.05 receive, MMS= $.25) in St. Maarten (Netherland Antilles), St. Martin, and St. Barth

Verizon International Roaming Rates

if you think you'll be using your phone a lot, you can sign up for Travel Pass for $10/day, with no per minute charges or data usage charges

Verizon Travel Pass - $10/Day

then of course if you're on wifi, you can use WiFi Calling for free, which allows your phone to act as if you're in the US....calls to/from US are free, but calls to/from SXM will be billed at the "pay as you go" rates linked to above