First off - you need to understand that beach front is now running $400, US per beach foot. So you have to take how many units are on a lot and figure that cost in.
Lagoon lots are not as much but not cheap and they can be really nice.
After you figure the cost of land you can they start thinking about building cost - remember - everything has to be brought out here by barge. Then if you are north of the cut it has to be barged, along with vehicles to transport it once the barge is docked, to the property.
The laborers still are not paid much considering what the cost of living is for them here.
But all of this is only money. The real issue here is time!!!
Before you pick a builder or a project ask around about their previous projects. Quality of work is very important here. If money is no problem and you really don't care how long it takes to have your place completed - then you can sit back and join the gringos laughing and drinking their Belikins.