I certainly never buy jam any more. I make plenty to last all year, and some to give away, from our blackberries, strawberries, apples and gages. I don't buy fruit for puddings either because I've always got gooseberries, apples, blackberries and gages in the freezer, ready to pop into a crumble or pie. And this year I've managed enough garlic and chilli to last us all year as well. We haven't bought potatoes for several months now, though we'll need to buy a sack for the winter. Not sure about the tomatoes until I've converted them into passata, sundried, pasta sauce, etc, but we've got enough of them for several months' cooking, obviously not for salads.
I think the other benefit I've had from growing my own fruit and veg is that it's changed the way I cook. You have to be more creative when you've got a glut of something. Our meals have gone from being focused around the meat to being focused around the veg, if you see what I mean.