My grandfather brought up 3 kids on 100 rented acres, and a productive vegetable garden was an essential to survival, not an option. Crow pie and baked pike were also local items on the menu in the 1920s and 30s.
My father didn't ever really farm, but trained in horticulture, and always had a very productive veg garden such that very few veg were bought.
We grow 95% of our own fruit and veg, eat our own lamb & mutton, have enought hens to sell a few eggs as well as meeting our own needs, and also sometimes get local venison, to say nothing of the occasional wild goose, and of course pigeon pie.
Being 80% self sufficient is quite easy and probably financially worth while as well as for quality of produce reasons. Being 100% self sufficient is either a lie, or only for serious nutters