US$500 savings doesn't make much sense unless the ticket originally was very much overpriced. Check out JetBlue from NY that has flights into Santiago that is much nearer.
If you decide to fly into Punta Cana, be sure to book a night in Punta Cana so you get to relax and enjoy that beach also.
Then plan on spending an entire day on the road to make it to Cabarete and another day to make it back. If you take the express buses (one from Punta Cana to Santo Domingo) and another from Santo Domingo to Sosua (then it's a short distance to Cabarete) you can do it under RD$500 -- but note you will be traveling for around 12 hours. Also, your flight would have to come in really early so you have time to catch the last bus to Sosua.