"Even if Berkshire's stock holdings and wholly owned subsidiaries perform only the same as the S&P, Berkshire still has the advantage of low cost leverage."

If we're trying to predict Berkshire's future performance relative to the S&P, we also need to predict the return of the S&P. During the go-go years 1996-1999 the S&P 500 returned 26.4% to Berkshire's 15.0%, but durning the period 2000-2022 the S&P returned 6.3% to Berkshire's 9.6%. My guess is that over the next decade the S&P will have a relatively low return, maybe 5% or so, and that Berkshire will outperform the S&P by 3 percentage points or so. That's just a guess, but the point is that value stocks, and Berkshire, tend to outperform the S&P when the return of the S&P is low and underperform the S&P when the return of the S&P is high.