Subject: Re: brk weakness caused by ,
Actually it's lower at $34.25
...
Is that for the shares sold in Q2? What is the source of that figure?

The $34.25 is right.
The best source is the 2021 annual report, as I believe there were no material buys after that date. That says 907,559,761 shares were owned beneficially for a total cost of $31,089 million, which is $34.2556 per share. I guess you could subtract the after-tax amount of all dividends received to date, if you wanted to figure out the breakeven spot.

There is no need to try to figure out which subsidiary it took place in. The shares are fungible, so the only thing that matters is the average price paid. As a general rule, this is true for every purpose except a US individual tax return, I think : )
It does get complicated if you do alternating purchases and sales, but that isn't really the case here.

Jim