We bring food down when on vacation. Yes we save some money over the two weeks and we have more to select from on the mainland so perhaps we feel the selections are a little better. Mostly we do it for convenience of not having to shop for these and concentrate more on local veg, fruit, spice, etc. Some spices we like are not readily available on STJ so we bring some of them as well.
While prices are somewhat higher for most and very high for some compared with mainland, I find the relative "pain" depends on where you live back home. That said, I never feel buying food on STJ is a vacation breaker by any means. You are in a beautiful place with wonderful people and you are on vacation. Spending a few extra bob on food is to be expected for what you get in return.

Now if you find yourself in CA on STT in a jewelry store with your wife...

I don't believe there are refrigerators/freezers there, only ice chests, so any frozen food you bring with you isn't going to last!

True, but I'm thinking we'll only bring 4 nights worth of stuff and we'll start the first night. That'll get the trip off to an economical start and save the dining out for when we've been there a bit. A cooler with ice should be okay, wouldn't you think? Feedback definitely welcome. By the way, once we fly into Charlotte, are there taxis right at the airport that can take us to the downtown ferry? How long a trip is it, do you know? I think the ferry stops at 5:30 pm. We're to arrive at STT at 2:44 pm if all is on time. Bonnie 😎

Bonnie-
I'm very excited for your & yours' plans!
Even if you freeze everything, like you said, it's not much, it might just be easier to buy down there, unless you're bringing a cooler.
Unless you take the time to pour ice on your goods constantly. It gets hot on STJ.
Believe it, or not, ice can be costly!
Bring your "check-in" soft-sided cooler with you, that within you can bring back keepsakes for your trip home.
I have to be honest in saying that I've never camped there; but if there's no fridge, you might be lugging down more than necessary, and Cinnamon isn't too far from essentials.
Ice
Grill
Fresh food
Water
Cold beer
Deet,
Repeat.
Can't wait to read your Trip Report!
One last thing,!
Don't forget your
Smiles-
MJ
:-)8-):-)8-):-)

I would not plan on more than 3 days at most and that assumes it is still frozen when you get on STJ. As mahojim said, ice can be expensive and doesn't last long depending on the cooler/location. The key is to stay out of the cooler keeping the cold in as long as possible.

You might be eating really well on day two.:-)

We might be having shrimp for breakfast even! That said, I did find a perfectly sized well insulated soft cooler in the market here on Cape Cod today. I'm chilling or freezing everything that I am putting into it including peanut butter and jelly, mayo and mustard, drink boxes and the meat/fish will be frozen solid. Will stick in a half gallon container block of ice and check the cooler through. Yah never know.
Regardless, we certainly will be smiling ear to ear in a few days. It snowed here today and may snow more tonight. It's beautiful but enough. Time for some tropics. Thanks for all the great advice. :@)

We're back and happy to report that we had a fantastic time and the frozen and cold food did well on our trip. Cinnamon Bay campground provides a large cooler and we transferred our stuff, added a block of ice and had scallops, shrimp, chicken and steak for our first 4 meals. Then we ate two dinners up at the campground restaurant and found it good and reasonable. We did a little shopping at the Dolphin Mkt and also had my birthday meal at The Lime Inn. We actually did do more than eat - the snorkeling was wonderful but we had to go to the South beaches for the first 1 1/2 weeks due to high surf at Cinnamon Bay. It was beautiful, though, to hear the surf all night long from our tent. We are already signed up for 2 weeks in March next year. And it snowed here on Cape Cod today....