For 4 adults 10 days we spend $450 ish for initial food. We are not big drinkers so add on what you think you will need for 7 days. We usually do steak, chicken, pork chops for the grill, tacos or burgers. There are opportunities to reprovision along the way so don't overdue the initial trip. If you try to buy 3 loaves of bread 2 of them will be moldy before the first one is used up!! We do cereal, yogurt, fruit for breakfast. If someone wants eggs they can eat ashore. Lunch is sandwiches, leftovers, salad. We always buy lots of chicken and grill it the first or second night. Leftovers are great for lunches, salads etc.
You can re provision at Sopers, Virgin Gorda yacht Harbor, Leverick and other places along the way