SpaceX shares closed below $135 this week, breaking the price Elon Musk set unilaterally for the company's May IPO. The stock traded as low as $133.80 on Thursday before recovering to $134.20 at Friday's close. Short interest climbed to 8.2% of the float, up from 2.1% at listing, according to S3 Partners data.

Musk priced the offering himself on June 3rd, announcing the $135 figure in a post before investment banks had completed their bookbuilding process. The move eliminated the traditional price-discovery mechanism that typically involves anchor investors, roadshow feedback, and underwriter judgment. SpaceX raised $6.8 billion at that price, valuing the combined space and AI operations at $243 billion. The company's Starship program and its neural-interface subsidiary drove the valuation, but neither segment has reported GAAP profitability.

The below-IPO trading matters because it isolates a structural question: whether founder-determined pricing can survive contact with liquid markets. Traditional IPOs underprice by an average of 18% on day one, a transfer of value from the company to first-day buyers that Musk explicitly rejected. His pricing method kept that $1.2 billion in implied discount inside SpaceX's treasury. But the mechanism assumed that Musk's own valuation judgment, grounded in internal models and long-term product roadmaps, would hold against public mark-to-market pressure. It has not, at least not yet.

Short sellers are testing two specific vulnerabilities. First, the $243 billion valuation implies Starship reaches commercial cadence by late 2027, flying 40+ missions annually at gross margins above 60%. Any delay in FAA licensing or propellant-depot deployment pushes revenue out and compresses the multiple. Second, the neural-interface unit, which contributed zero revenue in 2025, carries an embedded valuation of roughly $40 billion based on analyst teardowns of the S-1. That figure assumes human trials scale to 500+ participants by year-end 2027, a timeline the FDA has not confirmed. Shorts are betting one or both assumptions break.

Operators should watch three catalysts in the next 90 days. Starship's IFT-9 mission, scheduled for late September, will attempt the first payload deployment to lunar orbit—a milestone that either validates the $135 price or exposes technical lag. The company also faces its first quarterly earnings call in mid-October, where management will either reaffirm the 40-mission cadence or revise it. Finally, any FDA communication on neural-trial expansion will move the stock, as the $40 billion embedded value hinges entirely on regulatory clearance.

Musk posted Friday evening that SpaceX will "outvalue Earth" within a decade. The stock closed Monday at $136.10, back above the IPO price, though short interest remained elevated at 7.9%.