I've tried to cut out my food shopping bill by growing all sorts of food.
even high density seasonal planting ( I live in Florida so I got year around )
with a family of 4, could not get the veggie bill down to zero every week
on 20000sq feet of ground ( about 1/2 acre ).
BUT i got it down to 200ish for the year. ( we are at something like $2000 for organic )
I think it's just like you said, canning and storage skills
now the good thing is, I got almost all my neighbors to plant fruit trees...
Mangoes, avocados, oranges, lime and some others.
7 years from now we will have a well feed area