Now at $403 billion even after the recent apple sales (although it is likely more has been sold over last few weeks).

Two simplified book-end perspectives on the value (to its owner) of publicly listed securities:

1. For a long term holder without the possibility of monetizing the stake: business valuation is the only way to go because you are interested only in what the business can provide to you between now and judgment day. Market prices are less relevant (they may still impact some business decisions like capital raises or employee ownership plans).

2. For an owner of a small stake of stock in a tax free account (small enough to be sold in an instant - think retail investor): you may still engage in business valuation and conclude the stock is worth more than its price. But the current market price is the best proxy for the minimum value of the stock to you. After all you can instantly convert it to cash at the current market price.

To an owner of Berkshire Hathaway, the value of its stock portfolio has remained closer to the category one camp - I can't impact its sell decisions and the CEO's favored holding period is forever. They have also historically been reluctant to sell for business valuation reasons, e.g. KO in late 90s. But with recent apple sales (although tax was offered as to the reason for selling), I think its warranted to move a bit closer to category two and let ourselves be somewhat more informed by market prices than by business valuation when answering the question "what is it worth to me".