U.S. tech megacaps slide as SpaceX extends slump, AI expense concerns grow

June 22 (Reuters) - Shares of U.S. technology megacaps tumbled on Monday as SpaceX fell for the third straight session and hyperscalers Alphabet and Amazon looked set to lose billions of dollars in market value, driven by AI spending concerns.

SpaceX slid over 10% after last week's blistering post-IPO rally. The Elon Musk-led firm said it is launching a notes offering on Monday.

Alphabet dropped 6%, set for its biggest one-day fall since May 2025 and on pace to erase more than $256 billion in market capitalization. Google DeepMind's senior research scientist and Nobel laureate John Jumper said he was leaving for AI startup Anthropic, the lab's latest high-profile exit.

"This is more of a broader sector pullback on ongoing anxiety over tech companies' massive capital spend on the AI infrastructure," said David Wagner, head of equity and portfolio manager at Aptus Capital Advisors.

Amazon.com lost 4.8%, while Meta Platforms and Microsoft eased around 3% each. The three stocks together were set to lose more than $248 billion in market value.

Hyperscalers have committed billions to scale up their artificial intelligence infrastructures, though clearer evidence that AI products can generate returns that justify the spends are yet to be seen, raising concerns among investors.

Meanwhile, shares of most chip-related stocks were higher, with memory chipmaker Micron Technology leading the way with a 5.8% gain to hit record highs. Micron also announced a strategic agreement with Anthropic to scale next-generation AI infrastructure.

"There's a distinguishing aspect of this market between those who are receiving the checks, like memory names and those who are writing the checks," Aptus Capital Advisors' Wagner said.

Micron and other data storage companies SanDisk and Western Digital are the best-performing stocks on the S&P 500 so far this year, emerging as the biggest winners of Wall Street's hopes of robust AI-related demand.

(Reporting by Shashwat Chauhan and Twesha Dikshit in Bengaluru; Editing by Joyjeet Das)