Las Vegas is a pretty unusual place. There are some parts of Vegas that are inexpensive but a lot of very expensive bars, restaurants and hotels. A lot of people go to Vegas and spend way more money then they would spend at home. What is actually legal in Nevada is legal outside of Las Vegas. It is not legal inside the city of Las Vegas. Of course there is a lot prostitution going inside Las Vegas but it is not legal.
But if you walk around the nice casinos and areas of Las Vegas it does not have a seedy feel to it. It is very nice. I think the difference is walking around Sosua at night it does not feel upscale. People spend some much money in Las Vegas a taxi driver told as at the time he would get $50 a person to bring people to one of the Strip Clubs. The strip club would lose some money when you walked in the door but they knew on average they came out ahead.
Some of the pool party you have to spend a lot of money to have a cabana. At XS a cabana on the weekend on the upper level you had to spend $5000. Some of the other cabanas cost more money. They just have some many people spending crazy amounts of money they can afford to have really nice places, the best DJ's, nice restaurants, etc.
You can't compare Las Vegas to many places because of the amount of money that is spent there. They are not making it legal there but the "what happens in vegas stays in vegas" is working very well. They want the gamblers but they also want the partiers that spend a lot of money going on. It is happening in Vegas for the people that are willing to spend the money and like that type of atmosphere.
Sosua would have to have a different strategy because it is a completely different place. If they keep all the working girls or get rid of the working girls it would need a different game plan then Vegas.