I do wish them the best of luck. If it was available here I would order a loaf every day. Our household tears through a loaf of bread in a day and sourdough is my favorite.
Most delivery places require $10/min tickets. A 20 min delivery is a 40 min round-trip. @$9/hour for the delivery guy, that is $6 in costs. In other-words, -$1. This is before you've paid for the actual product.
That doesn't even get to the question of "cross-town" traffic in SF. Without some sort of multi-point distribution getting accross town in 20 min would be "interesting". Mission + SOMA of course NBD.
Of course the improbability drives the PR value. Somewhere between "too good to be true" and "will it break, in an interesting way?".
This works fine in Sweden which has a deregulated taxi market (=no shortage of available taxi drivers), but it wouldn't work in SF which has such an artificially constrained supply.
If they get funding they have the staying power to test the market and potentially find profitability. That's the big big advantage of using "OPM" when starting a business. Not guaranteed but not a non starter either.
One big benefit of starting at a low price below costs (if you can) is that it keeps others out who think "we can't make money doing this".
The trip may take marginally longer than if just one order were being delivered, but it ends up fulfilling five or six orders with one trip. The cost per order ends up being decreased to a reasonable level.
Tartine has been regarded as one of the best bakeries in SF for a number of years, having cultivated its reputation and following for over 10 years. It commands high prices not just because of quality, but also by its brand.
This is relevant not merely to pick apart your example, but more as a sort of chicken-and-egg challenge that faces many food service businesses. By default, bakeries are a low margin businesses, making it difficult to survive the long years you need to build the reputation that enables higher margins. The businesses that have circumvented this struggle have done so by such means as owner/chef fame.
With that said, I'm confident there are other ways of quickly achieving high-margin status. OP's company will have to be clever in doing so. It's unclear to me that delivery is a sufficient vehicle in this respect, except in bulk where ACME dominates.