Disclaimer that if you own any of the popular market-cap-weighted index funds (VOO, VGT, VTI) you are exposed to this risk and, conversely, have benefited from this ballooning in valuations.

NVDA, AAPL, TSLA and PLTR are together ~16% of VOO at the moment. NVDA alone is ~8%. Berkshire Hathaway is about the same % as TSLA, 1.61%.