Apart from Palantir and Tesla, the other big companies are trading at what would historically be considered reasonable P/Es given their growth rates and profitability.
What's really changed in the last 20-30 years is the incredible profit generated by the tech industry, and the defensive moats the biggest companies have built.
Palantir, possibly the most overvalued company on the stock marker, has P/S 63 and P/E 144.
Nvidia has P/S 21 and P/E 33.