“It’s interesting to ask why we find it offensive that Wal-Mart pays a single mother $9 an hour, but we don’t find it offensive that Apple pays a young man $12 an hour,” Mr. Osterman said. “For each company, the logic is the same — there is a line of people eager to take the job. In effect, we’re saying that our value judgments depend on the circumstances of the employee, not just supply and demand of the labor market.”

Twenty-two-year-olds also tend to be more tolerant of the Apple Store’s noise and bustle, yet these days some former employees describe a work environment that was too hectic and stressful, thanks in large part to the runaway popularity of the iPhone and iPad.

Managers often tell new workers that they hope to get six years of service, former employees say. “That was what we heard all the time,” says Shane Garcia, a former Apple Store manager in Chicago. “Six years.” But the average tenure is two and a half years, says a person familiar with the company’s retention numbers, and as foot traffic has increased, turnover rates in many stores have increased, too. Internal surveys at stores have also found surprising dissatisfaction levels, particularly among technicians, or “geniuses” in Apple’s parlance, who work at what is called the Genius Bar. Apple declined requests for interviews for this article. Instead, the company issued a statement:

“Thousands of incredibly talented professionals work behind the Genius Bar and deliver the best customer service in the world. The annual retention rate for Geniuses is almost 90%, which is unheard-of in the retail industry, and shows how passionate they are about their customers and their careers at Apple.”

That 90 percent figure sounds accurate to Mr. Garcia, who quit last July after four years with the company, overwhelmed by the work and unable to mollify employees and customers alike. Plenty of technicians do, in fact, like their jobs, which vary around the country, and which pay in the range of $40,000 a year in the Chicago area. Many technicians, though, wanted to leave but were unable to find equivalent work, according to Mr. Garcia and other former managers, in part because of the weak economy.

The problem for Apple Store employees, they said, wasn’t just the pace. It was the lack of upward mobility. There are only a handful of different jobs at Apple Stores and the most prestigious are invariably sought after by dozens of candidates. And a leap to the company headquarters is highly unusual.

Apple prohibits its staff from talking to the media, but several former employees who spoke for this article said they had fond memories of their jobs, and regarded them as ideal for people in their early 20s who aren’t ready for a full-on dive into the white-collar world.

And “Apple” can be a strong credential to have on a résumé, these people said. Technicians often move on to higher-paying jobs in information technology, they said, and sales staff have a leg up on the competition if they stay in retailing because “people know how grueling the job is,” as one former manager put it.