This is an aside from someone who is (trying to do) a CSA (community supported agriculture) this year.
Farming is hard. Small scale farming is bloody hard. We were planning on doing 20 boxes but only sold 12 (poor marketing on our part, but lucky because the land we're using is baad. Like, heavy clay, full of weeds, surrounded by groundhogs and turkeys). Anyway.
My point is this - it is not possible to sustainably grow tomatoes for what mom & pop sell them for. It's fine to grow them at home, but if your local farmer is to be paid a living wage (and not have to take on the debt to put up polytunnels/greenhouses and heating systems) it is bastard hard to do it.
So, not "as charity" but in terms of supporting the crazy people who do do it, I'd say find a local farm you like and buy some stuff from them. We need them to keep on.
Or learn to grow a chunk of stuff at home, if you can. Eat in season.
Because I can guarantee you, the stuff at the grocery store is grown in ginormous plantations or factories with underpaid overworked people, pesticided not when necessary but on schedule because it's more economical (though more destructive) to do that, tomatoes shipped green and gassed to make them ripen.
Don't get me wrong. I used to be WAY more into organic than I am now. I've seen how much killing goes on on small scale organic places (I used to be vegetarian. After a season of squashing bugs... meh. Cows > bugs? Sure. But.. they are on the same chart, right?).
Anyway. As others have said, it's not either/or.