A bet against Nvidia is smart. A bet against Palantir is not. Palantir has become deeply integrated into the surveillance states of America, and won't be going anywhere anytime soon.
It doesn't matter if it's the best firm ever and will get its dividends forever. You still calculate reasonably.
People say this kind of thing about Tesla as well, and Tesla has been stuck as a slightly-smaller-than-Mercedes-Benz sized firm for years and will stay like that forever, or even shrink relative to MB.
NVIDIA has a much more reasonable P/E ratio, even though it is of course very high.
This isn't a matter of rules of thumb. This is what's required to have prices that do not create an arbitrage opportunity.
I'm old enough to remember it being impossible to imagine a world without the USSR in it.
Both companies are growing revenue at a similar rate (~50% YoY), and Nvidia has a higher net margin, however Palantir's share price is up 717% over 18 months, whereas Nvidia is only up 124%.
It's hard to argue Palantir's valuation reflects its fundamentals, even if you believe Palantir will be benefit from lucrative government contracts for years to come.
Buying companies at 80x revenue has not historically been a great way to make money, unless they're growing revenue at several hundred percent per year.