Think SpaceX's $28.5 Trillion Idea Sounded Crazy? Wait Till You Hear What Anthropic Says.

Two months ago, Elon Musk made a bold claim. (I know. Shocking!) Explaining in its initial public offering (IPO) prospectus why Space Exploration Technologies (NASDAQ: SPCX) was justified in asking investors for a valuation more than $1.5 trillion, Musk & Co. asserted that, in the not-too-distant future, its products and services would serve a $28.5 trillion market for space, connectivity, and artificial intelligence (AI) services.

And the biggest of these was AI.

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According to Musk, AI is a market opportunity of $26.5 trillion.

SpaceX argues, Anthropic echoes

Such a gargantuan number obviously stuck with me. And when another AI company -- Anthropic -- announced last week that, in its opinion, the total addressable market (TAM) for AI services could reach $30 trillion, well, that rang a big bell.

Anthropic reported $11.6 billion in revenue in the second quarter (Q2) of 2026, more than doubling year over year. According to The Wall Street Journal, the company earned a "small operating profit" as well. But Anthropic sees even bigger things ahead for it as its TAM swells to $30 trillion and beyond.

So, $26.5 trillion? $30 trillion? These are big numbers, and they're suspiciously close to each other. But that's not the only thing they have in common. Anthropic says it's targeting a TAM comprising "the full scope of work that could be completed with AI models," according to the Journal. And it can reach this TAM if it can "theoretically capture ... 100% market-share."

Emphasis on "theoretically."

But here's the problem: Estimating the size of a company's TAM requires "a bit of guesswork," says the Journal. Rarely does the company approaching an IPO tell you exactly what it includes in its TAM. Even more rarely does it tell you when it expects to achieve the TAM it cites.

Unlike actual market-share reports, says the Journal, TAM estimates are "especially squishy."

Which is another way of saying it's impossible to verify them before the IPO has happened -- by which time it may be too late.

Examples from history

Need examples? In 2019, ride-share company Uber (NYSE: UBER) told investors that its TAM was $6 trillion. But how much revenue did Uber actually pull in last year? $52 billion. Or about nine-tenths of one percent of what it cited as its TAM.