I agree with Sungoddess that you might want to look into resorts with multiple hotels. That way your guests can choose what price range works for them. As she said, the Palladium has four hotels, Iberostar has four and RIU has 5. There is a huge range in prices and amenities. I know RIU has some restrictions on how many guests have to stay at the hotel where you have the ceremony, but I don't think the others do. It might be worth checking out.
Also, that $900 quote for Moon Palace is actually REALLY good for that hotel. Just keep in mind that the Moon Palace in Punta Cana is becoming a Hard Rock Hotel this spring. In my opinion, its going to take some of the Caribbean feel away from the resort, but maybe its not that big of a deal.