This week's selloff in  technology stocks  underscores a gnawing anxiety among investors: What happens if you throw a big party and few people show up? The Nasdaq Composite Index has slipped nearly 3% this week as Wall Street frets over whether the trillions of dollars going into artificial intelligence will deliver the revenue and profit growth needed to justify that exorbitant cost. Goldman Sachs estimates  tech companies will spend $7.6 trillion through 2031 to build thousands of new data