Comment by panax

For Berkshire in particular most of this cash is part of the float for their insurance business which they need to have on hand and available to pay out for potential claims and they will only ever keep that part of the float in cash equivalents. Still they have a large amount of cash beyond what they need for the float which they attribute to lack of opportunities to invest in given their immense size and investing style. They also want to be able to be in a strong position in a downturn or crisis situation. Hoarding all that excess cash still presents a major opportunity cost for them, although now not as much as before with higher interest rates.