If you are dumping to own the market as a monopoly, and so is your competitor, and both of you are buoyed up by seemingly limitless investor finance, then all that happens is that investors' money moves into the customers' pockets.
People would not be willing to pay the price however.
An efficient economy doesn't mean you can do anything you can imagine is technically possible; it means that market rates with everything priced in properly will discover whether or not enough people value it enough to pay for it.
Local economies were functioning well before for years, you were getting food from around your area, which is perfectly acceptable and efficient.
Doordash works today because venture capitalists are throwing millions of dollars at it, and dramatically subsidizing the cost of the delivery.
In other words, you can do that today because someone else is willing to pay. The VC's money won't last forever though. The question is if the economies of scale it creates will be enough to reduce the cost of delivery such that it is a sustainable business.
Most available data says "Probably not."
You weren't willing to pay the unsubsidised price.
- delivery was under-served and over-priced, and taxis charged too much, often because of viciously expensive auctions for limited legal taxicab slots, with the city raking it in and the drivers having to recoup it from fares
- Uber and friends are exploitative dumping schemes that tighten the screws on their gig workers even while they firehose money at customers
I couldn’t get a taxi in Chicago with a full beard. Period.
I've always wondered what the extreme end of this could look like. It seems like here in London companies in this same area are popping up almost weekly in areas like grocery delivery, food delivery, ride-sharing, etc, and they almost all have absolutely crazy initial sign up discounts. I suspect there is an entire class of people that are effectively taking advantage of this and I wonder how much they manage to save.