Six companies assemble the physical layer of the artificial-intelligence buildout. They fabricate circuit boards, machine enclosures, build power distribution units and cooling loops, and integrate the finished server and switch racks that cloud operators wheel into data centers. They own none of the silicon and sell under no brand of their own. They are paid a conversion fee — a few cents of margin on each dollar of components moving through the factory — which is why revenue at these firms can double while profit does something far more ordinary.

In the last week of July, five of the six reported quarters and five raised full-year guidance. What happened next is the interesting part: at the three most levered to AI, the price attached to each dollar of gross profit went down, not up.

The month is really two sessions

Over the 30 days to 17 August the six averaged a gain of 11.9%. Remove each company's two best single sessions and that average turns into a loss of 3.5%, with five of the six negative. Two shared dates do the work. On 30 July all but one rose together, Sanmina by 12%. On 4 August every one of the six rose again. The falls were just as collective: Sanmina dropped 20.7% on 28 July and Flex 10.8%, the sessions in which investors turned openly skeptical of hyperscale capital-spending plans after Alphabet's report was panned. Over three months the group is slightly negative, and four of the six sit 15% to 28% below their twelve-month highs. The twelve-month gains — an average near 94% — were earned earlier in the year.

Three grew, and got cheaper

Celestica, the Toronto firm that builds switches, data-center interconnects and custom racks for the largest cloud operators, reported June-quarter revenue of $4.7bn, up 62.4%. Operating margin widened to 9.75% from 9.42%. Gross margin actually narrowed 53 basis points, so the improvement is scale rather than richer work. It raised fiscal 2026 guidance to $20.5bn of revenue and $11.30 in adjusted earnings per share, and disclosed two design wins with multi-billion-dollar 2027 potential: custom racks for OpenAI's Jalapeno accelerator alongside Broadcom, and a manufacturing role on AMD's Helios interconnect.

Its price against trailing gross profit nonetheless fell to 21.63x from the 26.26x this desk recorded in May, and to 16.42x on forward estimates. The proximate cause is a financing, not a demand shock: on 5 August Celestica sold 9,677,419 shares at $310 each, below the prior close of $362.76, raising $3bn to fund capacity. The shares fell about 15% the next session, and the moving-average trend reading that flipped negative on 12 August is that crash catching up, not new information.

Sanmina, contrary to its reputation as an industrial and medical shop, now derives 62% of revenue from cloud and AI infrastructure — $2.148bn last quarter, up 173%. Revenue rose 69.7%, gross margin expanded 160 basis points and operating margin reached 6.43% from 4.70%. It is the cheapest name here at 10.12x trailing gross profit and 17.9x forward earnings, with a 5.1% free-cash-flow yield. The shares slipped anyway after a revenue and earnings beat, on the working capital the ramp consumes.

Flex, which makes power supplies, busway and switchgear as well as owning the Nextracker solar business, grew revenue 20.6% — accelerating from 4% a year ago — with gross margin up 72 basis points. Its Cloud and Power Infrastructure unit ran a 9.7% operating margin with more than 90% of the next three quarters already booked, and Flex intends to spin it off as a separate listed company in early 2027. Its price-to-gross-profit fell to 17.30x from 21.42x in May.

Jabil is the exception in both directions

Jabil, the Florida manufacturer with 135,000 employees spanning cloud, automotive and healthcare programs, raised fiscal 2026 revenue guidance to about $35bn and lifted expected AI-related revenue to roughly $13.6bn, up 50%. The reported quarter was weaker than the story. Revenue growth halved to 11.8% from 23.1% the quarter before. Operating margin went backwards, to 5.09% from 5.15%, and operating income grew more slowly than revenue. Jabil has not held an earnings call since 17 June, so its 23.4% month contains no fresh results at all. It is the only member within 4% of its twelve-month high, and the only one whose multiple has not compressed — 12.51x gross profit against 12.77x in May.

The small two split the same way

Benchmark Electronics, a $3.0bn Arizona firm doing board assembly and system integration for defense, medical and semiconductor-equipment customers, shows the cleanest operating leverage in the group: revenue up 17.7% to $756m, operating income up 33%. Its advanced computing line grew 71%; aerospace and defense fell 12% on program timing. Management said lead times for complex parts dependent on TSMC have stretched to seven-to-twelve months from three-to-five.

Plexus, the Wisconsin builder of healthcare, aerospace and industrial electronics, is the clearest pass-through case. Revenue rose 28.1% but operating income only 14.3%, operating margin compressed 56 basis points to 4.70%, and net income fell 4.7%. The order book is genuinely good — a record $4.5bn opportunity funnel and $400m of aerospace and defense wins this year — but the shares carry the group's richest capital-structure multiple at 29.4x trailing EV/EBITDA on a 0.84% free-cash-flow yield.

What is not settled

Component inflation is the live variable. Server memory contract prices rose 90-95% in the first quarter and were guided up a further 58-63% in the second, with Gartner modeling a 125% annual rise. That inflates the revenue line of every company here at close to zero margin, which is why price against gross profit is the only honest comparison. The second risk is cash: Celestica's trailing free-cash-flow yield is 1.33% against $1bn of capital spending this year and a $1.5bn placeholder for next, and Sanmina told investors working capital will build as its accelerated-compute program ramps. The third is concentration — Celestica's top three customers are about 65% of revenue, worse than 51% — against 2027 consensus that has its revenue rising another 69% to $34.8bn on an analyst range spanning $29.9bn to $40.4bn.

The setup

Where it stands — Three of the six grew fast and de-rated; Jabil rallied hardest on decelerating results and no new numbers since June. Would confirm — Celestica's third-quarter revenue lands in its guided $5.25-5.55bn range with operating margin holding above 9%. Would invalidate — Sanmina or Flex reports gross margin back below the prior year, showing memory costs are not being recovered. Watch next — Jabil's fiscal fourth-quarter results, its first report since 17 June, due in September. Valuation — Celestica 21.63x trailing and 16.42x forward gross profit against 26.26x in May; Jabil 12.51x versus 12.77x.