The well-choreographed customs routine is part of a hidden bounty of perks, tax breaks and subsidies in China that supports the world’s biggest iPhone factory, according to confidential government records reviewed by The New York Times, as well as more than 100 interviews with factory workers, logistics handlers, truck drivers, tax specialists and current and former Apple executives. The package of sweeteners and incentives, worth billions of dollars, is central to the production of the iPhone, Apple’s best-selling and most profitable product.

It all centers on Zhengzhou, a city of six million people in an impoverished region of China. Running at full tilt, the factory here, owned and operated by Apple’s manufacturing partner Foxconn, can produce 500,000 iPhones a day. Locals now refer to Zhengzhou as “iPhone City.”

The local government has proved instrumental, doling out more than $1.5 billion to Foxconn to build large sections of the factory and nearby employee housing. It paved roads and built power plants.

It helps cover continuing energy and transportation costs for the operation. It recruits workers for the assembly line. It pays bonuses to the factory for meeting export targets.

All of it in support of iPhone production.

“We needed something that could really develop this part of the country,” said Li Ziqiang, a Zhengzhou official. “There’s an old saying in China: ‘If you build the nest, the birds will come.’ And now, they’re coming.”

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A 32-gigabyte iPhone 7 costs an estimated $400 to produce. It retails for roughly $649 in the United States, with Apple taking a piece of the difference as profit. The result: Apple manages to earn 90 percent of the profits in the smartphone industry worldwide, even though it accounts for only 12 percent of the sales, according to Strategy Analytics, a research firm.

It is difficult to tally the total value of government benefits for the Zhengzhou operation, or to determine the exact effect on the profits of Foxconn or Apple. The subsidies aren’t disclosed by the Chinese government or Foxconn. They aren’t available in public records. And Apple says it was not a party to Foxconn’s negotiations.

The confidential government records obtained by The Times detail multiple meetings over several years in which Zhengzhou city officials discussed their “support” for iPhone production, calling the benefits a “preferential policy.” The records offer a snapshot of those benefits, including the specific aid for Foxconn in multiple areas, like infrastructure, labor, taxes and exports.

As China’s largest private employer, Foxconn, a Taiwanese company, has enormous leverage in the negotiations for those incentives. The company’s size and scale — and the sway that they afford in China — is connected to Apple. Foxconn is Apple’s largest supplier. Apple is Foxconn’s largest customer.

The two companies are intertwined in Zhengzhou. When the factory opened, Apple was Foxconn’s only customer here. Even now, the American technology company accounts for almost all of the production at the Zhengzhou plant, where about half of the world’s iPhones are made. Apple is also the main exporter using the customs facility here.

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As the Zhengzhou operation shows, China not only provides a large pool of labor; it also offers incentives that would be difficult to replicate in the United States or anywhere else. The trove of benefits in Zhengzhou flows through the production process for the iPhone, from the factory floor to the retail store.

Foxconn receives a bonus when it meets targets for exports. Those subsidies, according to the government records, totaled $56 million in the first two years of production, when the factory was exclusively dedicated to the iPhone.

The bonus is small on each of the tens of millions of iPhones produced during that period. But the subsidies add up: The government records list more than a dozen other forms of financial aid at the Zhengzhou operation.

The Zhengzhou government eliminated corporate taxes and value-added taxes that Foxconn pays for the first five years of production; they are half the usual rate for the next five. The city lowered Foxconn’s social insurance and other payments for workers, by up to $100 million a year.