The major air gateways to Berkshires are Hartford/Springfield's Bradley International (BDL), Albany International (ALB), and Boston's Logan International (BOS).
For the most part, fares are quite competitive among all three airports. However, discount airlines -- such as Southwest, jetBlue, and Independence Air -- spur competition among other airlines serving similar routes. For example, it's often cheaper to fly to Bradley or Albany from other cities served by Southwest Airlines (such as Kansas City or Albuquerque) than to Boston. And it can be cheaper to fly into Boston from other cities served by jetBlue, ATA, and so on.