I've eaten a vegan diet right out of the chain grocery store for years.  It's as cheap as McDonald's, but it's not very interesting.  Lots and lots of corn and beans.  You just have to read labels and exercise discipline.  I can't afford the natural food market, it's true.  It seems like there's a elitist markup for just going into those places.  Actually, in terms of work, I can feed myself on about one wage-hour a day (and these are crappy wages, too) which makes modern America far and away the most affluent civilization that has ever existed.  It feels like cheating to be poor here.  People aren't fat because there's a conspiracy.  They're fat because it's adaptive in hunter-gatherers to level out good times with bad times, and we've just missed the bad times lately.
This was a most wonderful post. I think you've said all that needs to, and could, be said.

I thank you. :)

I generally eat vegan, except for the occasional meal out with colleagues, at conferences, etc. For me it is more like beans and wheat - and peanut butter. But hardly any corn.

How do you eat corn? I can hardly imagine living on sweet corn from the cob. Cornbread is great, but too much work for lazy me. Do you make a gruel-like bowl, like grits or something?

I've heard that corn needs to be treated with lye or some such to make the protein available. Isn't that what grits are about?

Anyway, I always like to extend my diet, so I would love to hear how you buy & prepare corn to make a part of your staple diet.

Try corn tortillas. Better yet, make them yourself. Get the corn masa (quaker oats makes great masa, really cheap), pat it flat, put it on the skillet for a couple minutes, smear whateve you want on it. It's delicious! And hardly costs anything. Freshness is everything.
I grabbed an aluminum tortilla press a few years ago, one of those things I should have done so years earlier.  Tacos in fresh tortillas are oh, so, good.  (Store dry masa in the freezer if you don't use it fast.)
Here's my approximate recipe for corn bread, and lye is not the only alkali you can use to treat corn.

Approximately 35 percent corn meal, 25 percent masa harina (lime-treated corn used in tortillas) and 40 percent whole wheat flour. Add about 3-5 percent soy flour for additional protein, more complete balanced mix of amino acids in the total protein content, and additional fiber; add a little wheat bran and oat bran for their obvious properties.

No white sugar. Use a mix of honey and molasses to sweeten. Baking power, egg, and bake.

I eat semi-vegetarian. I eat about 1 serving (the official 3 oz serving) of meat a day, of various types. I eat a lot of casserole-type stuff, with a mix of brown rice and boiled whole wheat berries, sometimes with whole oat or rye groats as well, as the base. Whole Foods has those all in bulk, and often for less than a regular grocery, if they're available. Some items are cheaper here in Dallas at Central Market.

I throw in frozen veggies from the traditional grocery store. I usually use an equal mix of frozen corn, frozen green beans and frozen mixed veggies. Sometimes I use other, specialty mixes.

I then fry diced chicken breast, or the 98 percent lean grass-fed hamburger beef I find on sale, along with any garlic, onions, etc. I'm using. Then comes additional oil, water, teriyaki, tomato sauce, whatever, is going to be the basis of a broth/stock/sauce.

Then comes the HERBS/SPICES. This is how you eat vegan/vegetarian/quasi-vegetarian without getting bored.

I make Indian and Pakistani curries, starting with Central Market, which carries three or four different types. Or I'll make garam masala. Or something Thai with peanut sauce. Or pesto. Or alfredo. Etc., etc.

Read labels and excercise discipline... I wonder about that. To be a responsible vegan, you have to be conscious about things like soy protein, B vitamins. And my impression is that to make tasty food with vegan ingredients takes more skill. It's not that it's impossible, on the contrary, I think fancy vegetarian food is generally much better than fancy non-vegetarian food.

So I wonder about vegan food being inexpensive. How do you manage that?