Micron Technology (MU) guided to an 86 percent gross margin on $50 billion in revenue for its fiscal fourth quarter ending early September 2026, plus or minus $1 billion. That implies just 14 cents of cost per sales dollar—a jaw-dropping number that demands scrutiny.

The company achieved 84.6 percent gross margin in fiscal Q3 (ended May 28). That quarter jumped 10 percentage points from the prior quarter's 74.4 percent, and 47 percentage points from 37.7 percent a year ago. Micron attributes the surge to AI data center demand outpacing supply, driving prices higher across its product portfolio.

Here's the problem: memory cycles do not stay at peaks. In fiscal 2018, Micron's record memory boom topped out at 61 percent gross margin in the final quarter. The next upcycle peaked at 47.3 percent in early September 2021. Neither approached 86 percent—a 25-point gap that has no historical precedent in the company's business.

What happened next matters more. From the 61 percent peak in fiscal 2018, Micron's margin crashed to 38.2 percent three quarters later, then 28.6 percent one quarter after that. The 2021 boom was worse: from 47.3 percent, the margin plunged to negative 32.7 percent within four quarters. Both reversals exceeded 30 percentage points in roughly one year.

Micron management is already warning of deceleration. CFO Mark Murphy said in June earnings prepared remarks that the fiscal Q4 margin outlook reflects "a meaningful moderation in the rate of price increases." The company's own guidance shows it: the 86 percent figure represents only a 1.4-point increase from Q3, versus the 10-point jump from Q2 to Q3.

The company argues this cycle is different. Micron has signed 16 customer agreements with three- to five-year contract terms, which it says provide stability and reduce downside risk compared to prior spot-market-driven cycles. That's the bull case—and it matters for the stock's longer-term risk-reward.

But the near-term question is unavoidable: if the rate of price increases is already moderating at 86 percent margin, how much upside remains? And when the inevitable reversal comes, how far down does it go? Investors should watch Micron's fiscal Q1 2027 guidance (due Sept. 30 after hours) for signs of sustained demand or early cracks. Contract duration is a risk hedge—but it is not immunity.