These Low, Typ, High valuations are just a crude estimate that I've baked into my stock-tracking spreadsheets.
In the columns Y, Z, AA I define the multiple used for the Low, Typ and High respectively.
These are multiples of the figure in column V, which is mostly EPS, but occasionally I use an alternative metric such as Book Value Per Share (as I do with BRK in rows 1 and 2).
For the full BRK.B valuation, I use BVPS in column V and set Low to 1.2 (the Buy-Back threshold), Typ to 1.5 and High to 2.0, which I estimate as a typical trading range that might be seen at various times during the course of a few years.
For other companies, I figure that a quality company with stable earnings that are similar to Free Cash Flow might be good value at an earnings yield of 8.5% (P/E = 11.76) which may represent a soft floor to the usual trading range, might typically trade at a P/E of 18 and might be richly valued at the High P/E of 30.
Thus, applying the multiples of 11.76, 18 and 30 to the look-through EPS of the investments per share, we obtain $38, $58 and $97 respectively in cells N7, O7 and P7.
These values are then used to color-code the actual look-through market price of the investments per BRK.B-share which as I type this is shown as $54.6592 in cell D7. This is just below the $58 corresponding to bright yellow, so is very slightly darker and greener than bright yellow.
Incidentally, W7 is the inverse of P/E so it's the Earnings Yield at the current Market Price expressed as a ratio rather than a percentage, currently 0.0591 which could be expressed as 5.91%.
Similarly, the same multiples are applied to the Operating Company earnings of BRK.B (net of dividends) to provide the Low, Typ, High values in cells N8, O8, P8 and these are used to color-code the cell D7 'effective market value of the operation company' which is currently $103.0908 (calculated as the current market price of BRK.B $157.75 minus the look-through market price of the investments per share in cell D7 $54.6592).
Row 9 adds up row 7 (look-through) and row 8 (operating). D9 shows that the market-values of these two add up to the market value of BRK.B. The effective EPS per BRK.B share (operating + look-through) is in cell S9 (and cell V9) at $11.1829. This is multiplied by 11.76, 18 and 30 for the Low, Typ and High estimated valuations/trading range. The effective Earnings Yield as a ratio is in cell W9, currently 0.0709 or 7.09%.
You will note that these valuations differ from the Book Value Per Share valuations on row 4 (or row 5) which come out lower, but these do allow a certain like-for-like valuation method so the degree of over-valuation of under-valuation can crudely be compared to other shares that can be valued on a multiple of earnings basis. This might help to some extent in deciding whether to sell some BRK.B to buy something else that's much more undervalued, for example.
By laying everything out on a per-row basis, I seem to have turned the two-column method into a two-row method.
By changing the valuation metrics for the operating part of BRK.B or the look-through shares, you could come up with a custom valuation of your own choosing.
If you wish to share your own estimate of placing a Low, Typical or High valuation on the operating part of BRK.B, I could implement that in another tab of the spreadsheet. Also, you could add a third element by choosing to value cash per share at a certain multiple (e.g. 0.9, 1.0, 1.1 corresponding to a cash drag discount at 0.9, valuing it as risk-free at 1.0 and applying an optionality premium at 1.1) then apply a different valuation of your choice to the operating company net of cash.
For example, if you have an estimate of IV calculated based on a rate you'd like to plug in, perhaps use that IV with a multiple of 1.0 as the High, use 0.75 for Typical and 0.5 as Low multiple. Typical is a 25% discount to IV and Low is a 50% discount to IV.
Variations of the two-column method seem to be:
1. Use the market value of the look-through shares and add a sensible valuation of the operating company
2. Use a non-market valuation of the look-through shares and add a sensible valuation of the operating company
I hope that the above clarifies how these figures came about and how crude they are - albeit that they're probably more 'consistent and objective' than the fluctuating market price of the portfolio constituents.