Subject: Re: question on starting position in brk-b
Buffett bought in volume at average price of 357 in September.

Plus 22 cents!
Worth noting that that's the average price paid specifically for B shares.
They were willing to pay 2.8% more for A shares on an equal economic interest basis.

Brk is neither very cheap nor very expensive now.

It is somewhat more expensive than usual. Based on historical average ratio of price to peak book, and making a guess of end-2023 book, it's around 8.2% more expensive than the average since 2008, for example. Using last known book from Q3, 12.6% more than average since then.

But sure, it's not wildly expensive in an absolute sense.
By one possible definition, "fair value" is the purchase price for any equity that would get you a return of Siegel's constant: about inflation +6.5%/year. If Berkshire had been fairly valued on average since 2008, the average one year return would have been about that number, rather than the actual number which has been inflation+8.8%/year. So by that reasoning, and observing that it hasn't been getting more expensive in any meaningful way, the average observed valuation level has been quite a bit cheaper than actual fair value.

Jim