Dollar-stores overcharge customers while promising low prices

Isn't it just the predators that care about stock price to enrich themselves? Couldn't a co-op exist which offered non-predatory pricing and didn't try to maximize their stock price constantly? And real estate in destitute rural areas is generally dirt cheap.

Of course this could be offered. But, no one wants to do it because it's a thankless job. And if you're going to do a thankless job, you'd probably rather get paid a lot of money to do it than very little

You're ducking the argument. The loot from predatory practices is quickly absorbed not just by the single player perpetuating them, but by their complements in the economic network -- complements which a competitor would have to deal with on the loot-enriched terms, which turn launders exploitation into a "necessity" and transforms any charity into a weakness that will ensure your replacement. That's what Nash Equilibrium is, and it's an elementary result of game theory that Nash Equilibrium can lie very far from the global optimum. Even the global minimum can be a Nash Equilibrium. We should aspire to do better.