There's a good interview with Michael Mauboussin[0] in which he mentions the power of regression to the mean and base rates. He gets those ideas from Daniel Khanmen, I think. Anyway, an appropriate price is impossible to predict ahead of time, but using reversion to the mean as your guide, you see that we're pretty overvalued right now.

We're above the mean earnings ratios, FCF yields, etc, while at the same time knowing that we're almost certainly in the first leg of a major recession, and a period unprecedented economic uncertainty.

I think the bear case is much stronger than the bull case right now.

[0] https://www.youtube.com/watch?v=X5xoKZBcS4Y