You can't increase housing supply without affecting demand. You also can't increase housing supply to meet demand ... unless you actually make the area so undesirable that demand itself drops, meeting you halfway.
In fact, interesting yet flawed theories of supply and demand are seldom used to justify some sort of "protect existing restaurateurs' oligopoly" law. That isn't to say that it isn't valid to limit the number or type of restaurant in any particular area for e.g. safety reasons. But that has to be process-based, not just a declaration that this neighborhood has enough.
You can't argue that allowing single-family structures to be replaced by e.g. townhomes in a reasonable fashion is somehow beyond us as a society.
That's not a change in demand, that's a change in market clearing quantity.
Conversely, increasing residential capacity increases people which increases demand for services for the people which creates jobs which creates demand for residential capacity.
> If more people go out to eat, restaurants will make more money.
In total, sure. Individually? No reason to expect that.
> You can't argue that allowing single-family structures to be replaced by e.g. townhomes in a reasonable fashion is somehow beyond us as a society.
Maybe one could could argue that (or argue that doing so "in a reasonable fashion" is self-contradictory), and maybe one couldn't. But its irrelevant, because that's not what any in this thread did argue.
What has been argued is that the naïve analysis of its effects on affordability considering it only as a supply change in housing without considering the less-direct effects that has on residential demand, demand for (and price of) essential infrastructure and services which factor in to cost of living, etc., is foolishly overoptimistic.
You are responding to a comment that didn't address your argument, because it's not actually a response to anything that you wrote.
The argument says "you can't argue" a point nobody argued for in the subthread it was responding to (or, AFAICT, anywhere else in the thread, or, for that matter, anywhere else ever.)
1) Allow non-local demand? Do people fedex overnight the food?
2) Significantly increase infrastructure load? Do people live at the restaurants when they're not serving food, and thus require schools, police, parking, roads, jobs, etc?
Even then, restaurants do create demand on the city, and they are managed via zoning laws.
A more accurate analogy -- claiming that high density development will bring more restaurant patrons, resulting in more restaurants opening, resulting in restaurant prices dropping.
In the long term: rent rises.
In DC proper, rents rose.
What do you call this, the Lewis Carroll school of economics?