I use a simple short-cut to sense check these estimates.

Almost exactly a year ago, Buffett was repurchasing shares at a maximum price of around $323 per B after which he stopped as the price increased.
Based on his remarks on repurchases and valuations beforehand, it seems reasonable to expect that he would only pay a price that was at least 10% below the lower band of his intrinsic value estimate at the time. So we could assume that a year ago the lower band of his valuation for Berkshire was around $358 per B.

I don't think it is particularly aggressive to assume that in the year since, intrinsic value has probably grown at least at 8%. That would make a current IV estimate around $386 per B.

The indicates a 20% discount at the current price.

For me, that is closer to buy rather than sell territory.