SpaceX (SPCX -1.74%) agreed on Oct. 8 to buy Grain Management's nationwide portfolio of 800 MHz spectrum. The rocket and satellite company says the airwaves will help its Starlink Mobile service reach phones indoors. SpaceX didn't disclose terms, but The Wall Street Journal put the price at around $8 billion in cash.

Investors in the big wireless carriers took the news hard. Shares of T-Mobile US, Verizon, and AT&T each dropped over 10% the next day.

SpaceX stock, though, hardly moved on the news, and it's dipped since. Shares trade near $146 as I write. That puts them about 31% under the record $211.39 close on June 16 and only about 8% over the $135 price set in SpaceX's IPO.

So, does SpaceX's move into the carriers' business make the stock a buy?

Image source: Getty Images.

SpaceX is paying to reach phones indoors

The deal covers up to 14 megahertz of paired spectrum in the 800 MHz band. SpaceX said it addresses one of the main remaining technical gaps for Starlink Mobile, as a low-band signal like this can go through walls. And the company said most existing phones already support the band.

That same week, the Federal Communications Commission (FCC) cleared SpaceX to launch 15,000 next-generation Starlink Mobile satellites. The Grain purchase itself still needs FCC approval.

Grain just recently bought the airwaves from T-Mobile, in a deal that closed in August, paying $2.9 billion in cash and its own 600 MHz licenses. This makes a direct comparison hard, but the reported price is well over the cash Grain paid.

The purchase comes on top of a bigger one, too. SpaceX is buying 65 MHz of spectrum from EchoStar for around $19.6 billion, a deal it expects to close at the end of November 2027.

Management's thinking on low-band spectrum also looks to have changed fast.

"You don't have to necessarily spend many billions of dollars in low-band spectrum all upfront before you deploy your system," President Gwynne Shotwell said in early August, on SpaceX's call to go over second-quarter results.

Around two months later, SpaceX reportedly agreed to spend about $8 billion on low-band spectrum. I'd say this suggests the company wants its carrier service in place earlier, even at a higher cost.

Starlink is where SpaceX makes money

Showing why SpaceX keeps investing here, revenue in its connectivity segment (which houses Starlink) rose 66% year over year to $4.3 billion in the second quarter. This was a sharp acceleration from 32% year-over-year growth in the first quarter, when the segment took in $3.3 billion. Operating income for the segment climbed 79% year over year to $1.7 billion.

Of course, that profit's carrying the rest of the company. Connectivity was the only one of SpaceX's three segments to turn an operating profit, while its space and artificial intelligence segments each lost money.

Starlink Mobile is tougher to size. SpaceX doesn't break out its revenue, which is part of enterprise and government sales, and it earns that revenue from revenue-sharing deals with partner carriers like T-Mobile. Owning airwaves could let SpaceX sell service directly. But it could also put SpaceX up against the companies it splits revenue with now.

Shotwell also said on the August call that SpaceX would start flying its next-generation mobile satellites next year and begin service at the end of next year.

Does $8 billion move a $2 trillion stock?

Not by itself. At today's price, SpaceX is worth around $2 trillion, and the reported $8 billion is under 1% of that. And the company ended June with $100 billion in cash, cash equivalents, and marketable securities.

The bigger concern for shareholders is the stock's valuation. SpaceX's revenue for the four quarters through June was around $23 billion, leaving the stock at more than 80 times sales. And the company lost $4.8 billion in the first half of 2026. SpaceX posts its third-quarter results after market close on Oct. 20.

Yes, selling phone service directly might become a meaningful new revenue source for Starlink over time. But this revenue is probably more than a year away, and it comes with the cost of building out a network.

In the end, the Grain deal makes Starlink Mobile a more serious rival to the carriers, and their share prices reflected that. For SpaceX shareholders, though, it's a small and far-off addition to a company valued at over 80 times sales. Even after a 31% fall from its peak, the stock looks too pricey to me.