Their sensational performances have been one of the top reasons the U.S. market has hit records despite a slowing job market and high inflation. Their prices have shot so high, though, that critics say they're reminiscent of the 2000 dot-com bubble, which ultimately burst and dragged the S&P 500 down by nearly half.
Nvidia came into the day with a 4.6% drop for the month so far, for example, after its stock price more than doubled in four of the last five years. The biggest player in AI chips swung between gains and losses throughout Wednesday. Palantir Technologies, another AI darling, fell 3.6% for one of the day's larger losses in the S&P 500.
Similar questions about priciness are dogging the rest of the U.S. market, though not as pointedly as for Big Tech and AI superstars.
One way for stock prices to look less expensive is for companies to deliver big growth in profits.
On Holdings jumped 18% after the Swiss shoe and apparel company reported a much bigger profit for the latest quarter than analysts expected. It reported growth in sales from around the world, with the strongest coming from Asia.