I learned that if you book directly with an airline, most of them have a price drop guarantee. US Airways is the only one that appears to fly direct from Philly to Punta Cana. Here is their policy:
Lower fare guarantee
When a new lower fare becomes available after a ticket has been purchased, customers are entitled to a lower fare guarantee refund within the following guidelines. We will deduct a $150 change fee ($250 for international travel) and apply residual funds in the form of a US voucher. Additional rules and restrictions may apply. Call reservations for a lower fare guarantee.
- The lower fare is available for the exact itinerary previously purchased.
- No portion of the reservation has been flown.
- Lower fare guarantee refunds are not available for online ticket exchanges. Certain promotional fares may be excluded.
SO, at least we would get a voucher for a future trip if we book now!