For real though, you don't plant your own tomatoes to save money, you plant your own tomatoes because your crop is going to taste so good that you'll be chasing that flavor any time you're stuck buying them from the store. Just so far beyond storebought.
It's the one crop I keep coming back to every year - the effort is worth it.
It's the same in that most fruits and vegetables you can buy at the store have been bred for quantity and shipping. Home gardeners can grow varieties that are bred for flavor. So my Nebraska Wedding Tomatoes may not survive a trip across the country with UPS, but they taste amazing. And my Double Gold raspberries don't produce bushels, but they're the best I've ever eaten. I do think I'm probably saving money growing garlic. Very low maintenance plant, and I grow enough to save what I need to plant for the next year. So some crops are pretty cost effective, but some are really for the flavor.
Not all, but most. I don't notice much of a difference with peppers or carrots, but strawberries especially are incredible when grown from a garden and pretty tasteless when bought from a store. Tomatoes don't have quite as significant of a difference, but they're still much better. I don't think I've ever gotten fresh beets from anywhere but a farmer's market or my garden, so I'm not sure about them.
Personally, it's everything I grow. Tomatoes, green beans, peas, cucumbers, onions, asparagus & garlic. There's also that excellent feeling of if I don't feel like running to the store just for a vegetable and we've got everything else for dinner, I can just send the kids out to pick it. None of our peas made it into the house this year either because of the kids lol. We also have an herb garden with mint, chives, thyme, etc that the kids are free to graze whenever and it's especially great for those "I'm Hungry!" moments between snack & the next meal
More noticeable in Tomatoes, but everything is more flavourful. Potatoes are more Potatoey, leafy greens are more intense flavour, some people finding home grown romaine too strongly flavoured because they are used to it tasting like nothing