Looking at the annual report it's really interesting to see that their equity, fixed incomes and cash holdings are worth approximately $160k per share. That means at today's price you're buying the rest of the business (a mix of utilities, small industrials and retailers, leasing firms), and it's earnings of $12.3k per share for only $32k per share.
If you believe that the companies they own will mirror the performance of the market as a whole (baring in mind they've done quite a bit better over the past decade), then that's a big discount on an index fund.
Using data from here (
http://www.multpl.com/):
S&P500, BRK, % discount
P/E: 21.49, 12.8, 40.5%
P/B: 2.62, 1.63, 37.8%
I adjusted Berkshire's book value down to take into account that they record the value of their financial holdings at market prices rather than the underlying companies measures of book value. This
increases the P/B reported for them here but I think it more accurately reflects the value of the company. You could also remove their net liability of insurance float as it's been consistently profitable since it's inception