NEW YORK, July 30 -- The number that sent Meta Platforms Inc. META stock down as much as 7 percent in after-hours trading Wednesday was not $60.8 billion. That was the quarterly revenue figure, up 28 percent year over year, a result that would have been celebrated in any other earnings season. The number investors focused on was $784 million: Meta's free cash flow for the quarter, down 91 percent from $8.55 billion in the same period a year ago. The gap between those two figures is Mark Zuckerberg's AI spending program, still accelerating, still without a return timeline, and increasingly testing the patience of shareholders who have backed the bet for three years.

The quarterly results were complicated in the way that only a highly prof...