There are already DIY
yards in the USVI - at least on St Thomas - so that is not going to be a major factor - but total cost is a factor along with making more space available than the existing yards have. They have been known to fill up fast and you have to wait quite awhile to get hauled.
- - But unless you are a financial masochist running a boat
yard in anyplace subject to US environmental/OHSA/etc. rules and reg's is not a happy way to live and try to make money
. Move down island, invest in building a boatyard that employs locals and you will be welcomed with open arms and near total lack of rules and reg's. That significantly lowers your costs and raises your profits.