Barrons takes a stab at it:
Berkshire Hathaway Had a Strong 2022. What to Watch in 2023. | Barron’s (barrons.com)
Relevant piece:
We estimate that book value declined about 8% to $315,000 per class A share in 2022. The largest contributor to that decline was an estimated drop of more than 15% in Berkshire’s equity portfolio as Apple (AAPL), the largest holding at $115 billion or 40% of the portfolio, was off about 27% in 2022.
Currently:
1.47 x Barron’s estimated book value.
1.34 x peak book value.