Airfare pricing is mostly driven by demand...and yes, less capacity creates less availability but I did a little study using BOS-SXM 2nd Saturday (one week) R/T with no overnights or excessive layovers

Cheapest "normal" fare;

May...$615
June..$545
July..$777
August$701
Sept..$425
Oct...$583
Nov...$428
Dec...$468
Jan...$427

So there are still decent fares out there depending on when you want to travel AND how early you book that travel