Apple’s Growth Machine Is Slowing. High Prices Might Not Save It.

The Apple growth and profit machine is wavering, and the boost from price increases might not be enough to keep it going at historic rates. The pressure is on John Ternus to keep the momentum going.

The company saved the bad news for its earnings call, an hour after it posted its results for the September quarter, projecting that for the current quarter its high-margin services business will continue to slow and that its widely watched gross profit margin will continue to fall.

Apple AAPL -1.83%decrease; down pointing triangle shares had been flat in post-close trading but declined 4% after the company made the projections, which fell short of Wall Street estimates.

The impact of high memory costs are weighing even more heavily on the company, Ternus and Apple Chief Financial Officer Kevan Parekh said on the company’s earnings call. Apple has stockpiled cheaper components purchased earlier, but those inventories are dwindling.

When Ternus took over as Apple’s third chief executive of the past 29 years on Sept. 1, he inherited sky-high expectations. The men he followed were among the most successful company leaders in American business history. Steve Jobs revolutionized consumer devices multiple times. Tim Cook expanded Jobs’s creation to spectacular heights.

Investors have bid up Apple shares because it has been a port in the AI storm—a reliable and capital-efficient business that stands apart from rivals which are spending hundreds of billions of dollars racing to the AI frontier.

While others invest in data centers, Apple has been pouring its own cash into buybacks and dividends. But that safety may be challenged if Ternus can’t speed up Apple’s innovation engine.

Apple’s lagging performance in AI was evident when its new “Siri AI” chatbot arrived this past quarter. Its long-maligned assistant was already stale the day it arrived, surpassed by agents such as Instinct and Muse that can complete multistep tasks for consumers, while Siri still sets kitchen timers.

Apple needs to give people reasons to buy its devices as they get more expensive. The company raised prices across the board last quarter to help offset the skyrocketing cost of memory and storage chips inside iPhones, iPads and Macs. Without compelling new features, a big question is whether consumers will slow the frequency of iPhone upgrades.

The new iPhone Duo appears to be a bright spot. Consumers are scooping up the $1,999 foldable smartphone despite mixed reviews—so many that Apple can’t keep up with demand. Shipping dates jumped out to January soon after the device went on sale, a disappointment for the normally reliable Apple supply chain.

Apple said its revenue grew 12% in the September quarter, slightly ahead of Wall Street’s expectations. Its widely tracked gross profit margin, at 47.9%, also came in just ahead of analyst estimates.

Apple will need to find new growth avenues because a reliable engine during the Cook era—the services business—is slowing. Courts and regulators worldwide have limited Apple’s ability to charge developers big fees to distribute apps through its App Store, the biggest component of the company’s services segment.

Apple’s valuation has bumped up against a ceiling in recent weeks. Six times it traded above a $5 trillion market capitalization intraday before finally closing above the threshold, which it has already fallen back below.

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Write to Rolfe Winkler at Rolfe.Winkler@wsj.com