I generally agree that 1.2x BVPS is a steal for BRK and I'm normally prepared to project forward to the yet-to-be-reported BVPS, which might mean adding 2.5% to the previous quarter's BVPS much of the time. However, this quarter is different!
I'd agree with John Hjorth that BVPS as reported on 23rd Feb when the Berkshire Hathaway Annual Report is published is very likely to be around $143-$145 range after accounting for the US Tax Cuts, which have a disproportionately large effect on BRK's deferred tax liabilities and profits made in the USA. For me, $172 would be a screaming buy at about 1.2x estimate 2017Q4 BVPS.
I would say that at close price of $191.42, the market-value of the operating part of BRK.B is about $119 and that $72½ would be about the look-through market value of the portfolio of stocks including Kraft Heinz, BYD and Sanofi stocks that aren't included in 13-F reports.
Mark-to-market losses on the portfolio of stocks since 31st Dec 2017 would perhaps knock off 3-4% from their contribution to current running book value. Maybe there is as much as a 1.5% reduction in running BVPS would knock about $2 per share off the BVPS that will be reported for 31st December 2017, so I'd reduce that $143-$145 to around $141-$143 for BVPS, setting a 1.2x BVPS "soft floor" of around $169-$172, although the authorized buyback threshold would be any price up to 1.2x the actual last reported BVPS, not the running BVPS.
I personally think the US Tax Cuts have boosted Intrinsic Value of BRK.B by a little less than they've boosted Book Value, but I'm content with what I suspect will be reliable compounding at a rate that significantly exceeds our goals, hence our large exposure to BRK.B, especially in the absence of other high conviction ideas and my additions in Dec and Feb around $196 (GBP £141 - £147 depending on exchange rate) even when it appears on the surface to be priced at 1.5-1.6x BVPS.
Last night we checked our household budget and brought forward and increased our usual cash subscription to add another 1.5% to our portfolio, which should be available to invest today or possibly as late as Monday. I'm also considering switching our 4% position in Wells Fargo to BRK.B, so might well do both on the same day and add about 5.5% to our BRK.B weighting soon somewhere in the $191 region (GBP £137).