It is a lot, but depending on what you are buying, entirely believable. Longer shelf life and ease of preperation both increase prices, as does variety. Hard red wheat lasts forever, but if you don't have the know how to use it properly (a) learn, and (b) start with something easier, even if it more expensive. Canned butter and cheese, those both add up fast, as do canned or irradiated and wet packed meats. Then add in a few treats (a few cases of people's favorite soda, quick bread mixes, chocolate, a few bottles of good scotch, one good cigar per week per adult), and while it is bulkier and more expensive, it is more "civilized". It also gives you trade goods.

And if we are factoring in things that aren't "food", but consumables, into that mix, $4K is even easier to believe. Fuel, batteries, medicines, matches, they start to add up and they are all things that I would count in with the food myself. Now we'd probably all reduce the cost with a couple bricks of .22, a box or ten of something in the range of .30-30 to .30-06, fishing gear and some rattraps, but even that adds up pretty quick.