I honestly don't get the point of this company. If I feel competent to judge that some decision they make like investing in American Express is good, why not do that directly, myself?
Even if you look only their public stocks, Berkshire has certain advantages compared to individual investor.
They can buy a huge amounts of stock from pension funds with a discount to the market price. These kind of deals usually happen outside of public market so that the price din’t fluctuate due to the deal.
Also, individual investor can’t buy a public railroad company in its entirety. Berkshire did exactly that and continues to reap value from that deal, while individual investors of the said railroad company were forced to cap their long-term upside to the deal price.
but they have other business activities apart from their minority holdings, which you're ignoring.
they're also able to identify opportunities to take over (both private and public) companies entirely, and add value to those businesses in an active way that a small private passive investor is not able