Location, location, location!
Oceanfront or soundfront at sunset really are the most idyllic spots for a wedding on the Outer Banks...but in order to host an event there, you are going to have to rent absolutely everything. Some venues have tables, chairs, linens, kitchens, etc. which make catering easier and more affordable.
When booking your venue, be sure to ask about the availability of these items.
Some other things to consider are the availability and access to running water, waste disposal, ice, and whether or not the venue has a fee for using an outside caterer.
All of these things can affect your bottom line.