Your city to Nassau approx: $350 adv purch / sat stay round trip
alt: your city to Ft.Lauderdale, Bahamasair to destination
($326 Seattle to Ft.Lauderdale in mid-Feb)
Nassau(Ft.Lauderdale) to Eleuthera (or other island) approx: $128-$150 round trip
Lodging shared approx: $150 per some of the options found thus far
Approx cost for the week: $650 plus your personal spending.
I would assume that with $50 each we could fill the kitchen to capacity. We found a place in Georgetown where nightly BBQ specials cost $6 and you could barely walk if you got a side of peas and rice with a beer.
I might ask for the airline ticket for an Xmas gift, cutting my pocket spending down to about $300 while simultaneously getting buy-in from the commandant