Before we get to why many on-demand apps have struggled to achieve mass-market prices, it is important to remember why anyone ever thought they could: because Uber did it. The ride-hailing company that is valued by investors at more than $60 billion began as a luxury service. The magic of Uber was that it used its growth to keep cutting its prices and expand its service. Uber shifted from a convenient alternative to luxury cars to an alternative to taxis to, now, a credible alternative to owning a car.  Investors saw Uber’s success as a template for Ubers for everything. “The industry went through a period where we said, let’s look at any big service industry, stick ‘on-demand’ on it, and we’ve got an Uber,” said Hunter Walk, a venture capitalist at the firm Homebrew, which has invested in at least one on-demand company, the shipping service Shyp.  But Uber’s success was in many ways unique. For one thing, it was attacking a vulnerable market. In many cities, the taxi business was a customer-unfriendly protectionist racket that artificially inflated prices and cared little about customer service. The opportunity for Uber to become a regular part of people’s lives was huge. Many people take cars every day, so hook them once and you have repeat customers. Finally, cars are the second-most-expensive things people buy, and the most frequent thing we do with them is park. That monumental inefficiency left Uber ample room to extract a profit even after undercutting what we now pay for cars.  But how many other markets are there like that? Not many. Some services were used frequently by consumers, but weren’t that valuable — things related to food, for instance, offered low margins. Other businesses funded in low-frequency and low-value areas “were a trap,” Mr. Walk said.  Another problem was that funding distorted on-demand businesses. So many start-ups raised so much cash in 2014 and 2015 that they were freed from the pressure of having to make money on each of their orders. Now that investor appetite for on-demand companies has cooled, companies have been forced to return sanity to their business, sometimes by raising prices.  Look at grocery shopping. Last year the grocery-delivery start-up Instacart lowered prices because it thought it could extract extra revenue from supermarket chains, which were attracted to the new business Instacart was bringing in.  That has panned out only partway. A representative told me Instacart’s revenue grew by a factor of six since the start of 2015, and it has been able to use data science to find efficiencies in its operations. But the revenue from supermarket chains wasn’t enough to offset costs, so in December, Instacart raised delivery charges to $6 from $4 for most orders. It has also reduced pay for some of its workers.  The changes are in line with a drive toward profit. The company said it had stemmed losses in its biggest cities, and aimed to become “gross-margin positive” — that is, to stop losing money on each order — across its operations by the end of April.  Or consider delivery services. Postmates, one of the most established on-demand delivery start-ups, began as a premium service that charged extraordinary fees — 50 percent isn’t unusual — for the convenience of getting just about anything delivered anywhere. That premium has kept the company’s unit economics in the black. Postmates does not lose money on the bulk of its orders.  But high prices left the company vulnerable to lower-priced competitors, including the relatively newer entrant DoorDash, which has received piles of funding from Silicon Valley venture firms (the company announced a $127 million funding round on Tuesday after struggling to raise some of the cash).  Last year, Postmates began offering a cheaper service in which restaurants kick back some of the delivery fee in return for the promise of more orders; that price is $3 or $4 for a food order, not including a tip. But so far, that service represents 30 percent of the company’s orders. DoorDash, which charges $5 or $6 an order, has a similar business model, which charges restaurants a commission for each order.  Is a fee of $3 to $6 for deliveries of groceries or food a mass-market price? For many people, the savings in time is worth the price. But the median American wage is around $20 an hour, so a fee of even a few dollars is a costly premium.  Instacart, Postmates and DoorDash say they see opportunities for lowering prices as they grow. They are hoping for efficiency gains that come with volume, like bundling two or three orders in each delivery.  But it is wise to be skeptical of claims of future price cuts. Last year, Tri Tran, the founder of the food-delivery company Munchery, told me he expected prices for most dishes on the service to come in at under $10 a person. Today Munchery’s prices are pretty much unchanged. When I asked the company what happened, I got no real answer from a representative.  That brings us to Luxe. A spokesman told me that the problems I was seeing were caused by high demand. The company is growing at 40 percent every month, which has caused hiccups in service. Luxe has no further plans to raise prices and thinks its current model can generate significant profit margins, and lead to lower prices, as it scales.  As a user, I hope so. But I wonder. The lesson so far in the on-demand world is that Uber is the exception, not the norm. Uber, but for Uber — and not much else.  Correction: March 23, 2016 An earlier version of this column misstated Instacart’s projection of when it will stop losing money on each order. It is the end of April, not the end of the year.  A version of this article appears in print on March 24, 2016, on page A1 of the New York edition with the headline: Try as Silicon Valley Might, Uber’s Ways Don’t Translate. Order Reprints| Today's Paper|Subscribe
The ride-hailing service is a giant, but companies that aim to get stuff done on demand for customers, like food delivery, grocery shopping and parking, are faltering.