Casa de Campo is one of the nicest places on the island (depending on what you are looking for in a vacation/living area - not so great if you like surfing, but if golf is your thing you're set for example) with a price tag to match.
Great villas to stay in and the area is booming, it has changed drastically during our nine years here, they are even building a block of villas above the polo field now.
You have to be really well off, connected to friends with villas there or both to be able to afford to stay in CdeC on a regular basis.
Many of the posters here are a bit more budget travel oriented and/or looking for jobs on the island that pay so poorly (ie - "I want to teach English even though I don't have a teaching cert.") that there is no way they could ever afford to stay there more than once or twice.
To the best of my knowledge the average cost for a tourist family of four that rents a villa for a week long vacation there and does touristy things is not quite 10,000 USD. Of course some spend more, others spend less and this is averaging between high/low season rates.
If you ever get the chance to go take it and make sure to rent a golf cart to cruise around the grounds, it is a lot of fun.