Oh I like this! My kind of maths.
Soft fruit plants probably yield an even better return: the amount of money I've saved myself on strawberries, raspberries and blueberries from my allotment over the years is considerable - unfortunately it's the kind of thing I haven't been able to calculate precisely given time constraints, but it's several hundred $$$, with next to no financial outlay.
I'm especially a fan of raspberries: basically a 'weed' which just goes on giving with no significant maintenance required! And I love them, just love them!
Where apples are concerned, one of the most punishingly depressing things I see in my local supermarket are imported apples - I live in the 'garden of England' FFS where dozens of local varieties of apples grow... how many make it to the supermarket....basically none.
I love raspberries too! They are a weed! Oftentimes with things like raspberries they get a bit out of hand at relatives or friends place and you can get them for free.
There used to be a lot of fruit grown semi locally because transportation was slow and expensive. Every region had their own apple varieties for example.