To many investors, Apple Inc. (NASDAQ:AAPL) is a company that can do no wrong. AAPL stock has gained nearly 10% in value in just the past month, and since breaking out of its trading range a year ago, it is up 60% to add $300 billion to its market capitalization. At the moment, Apple is the most valuable company in the world, with a market cap of more than $800 billion.

This is wealth creation beyond anything ever dreamed of before.

Unlike the situation with other large techs, however, the money is spread widely. Vanguard is the largest shareholder, and current insiders tend to use Apple stock like most employees — as a source of cash rather than the root of vast fortunes.

The last time I wrote about AAPL, I called it mature technology, wondering if the valuation were stretched, asking what category it might open next to justify its valuation.

I should not have been so bearish. Sales of the iPhone in the first quarter were strong enough to keep the momentum of the stock going.

But Apple is on the horns of a dilemma.

Sales vs. Service

While Apple was the leading phone maker during the fourth quarter of 2016, it held just 17.8% of the market. Android phones held the rest, and the market grew just 3%.

Unlike its Android-based rivals, Apple gets a premium price for its proprietary product. It also makes a great phone. But its market share is limited to the number of people who can afford a great phone, and as growth moves into countries like India that’s limiting. AAPL is in fourth place in the fast-growing China market, and those makers have their eyes on India as well.

Apple’s refusal to compromise also threatens its fastest-growing business segment, Services. Apple has invested billions of dollars to build its own cloud network over the last years, and took in $7.172 billion in Services revenue during the first quarter. That’s 18% more than the same quarter a year ago.

Since services are tied to AAPL products, however, there’s a limit to that growth as well. With iPhone sales growing by single digits year-over-year, revenue from selling and storing content, or handling transactions, won’t keep growth at 18% much longer.

The Used Market

Apple is trying to hit lower price points in the U.S. by selling used, refurbished phones, but even here, the pricing only gets you to the top end of what its Chinese rivals sell new phones for.

In India, where the government stopped Apple from using this strategy, the company is selling its 5S, a phone from 2013, at the equivalent of $230. AAPL maintains high margins on these units because they only have 16 GB of memory, development costs are amortized and most sales are done online.

This also gets millions of people into Apple’s service ecosystem, the App Store, Apple Music and iCloud storage.

Bottom Line on AAPL Stock

The last time I wrote about Apple, I focused on the Apple Watch, calling health the company’s biggest bet. If it can get a non-invasive glucose test approved by the Food & Drug Administration (FDA), it could get millions of Apple Watch units prescribed by doctors.

There are, of course, continuing rumors about the iPhone 8, and what it might be called, as well as the Apple Car. Well, there might be an Apple Car. Or it might just be a transformation platform. The jury’s still out.

The company is squeezing Qualcomm, Inc. (NASDAQ:QCOM) on its radio chips, cutting costs to maintain margins, and its growth seems to justify a market-matching price-to-earnings multiple of 17.9. It profits from every part of the iPhone market, even the squeal.

But it should be noted that this is the highest P/E that AAPL stock has enjoyed since its go-go days early in the decade, and that the whole market is at a stretched valuation. A forward P/E of nearly 15 and a price/earnings-to-growth ratio of 1.5 seem similarly digestible in a bubble, but on the high side for Apple, historically speaking.

Apple is in a good, though not great, position as far as making the bull case from the business side of the argument. But that valuation is the lynch pin — and makes AAPL as vulnerable to a general pullback as any other stock.

Dana Blankenhorn is a financial and technology journalist. He is the author of the political polemic Saving Trumpistan, Restoring Democracy, available now at the Amazon Kindle store. Write him at danablankenhorn@gmail.com or follow him on Twitter at @danablankenhorn. As of this writing, he was long AAPL.