Stock price is not usually a reflection of anything except the general sentiment of the market. When the sentiments are high, even crappy shares are worth a lot and during bear market, even best of stocks sell below thier Book Value. Buying dividend stocks is two edged sword. On one hand, they give regular income but on the other they don't have much capital to expand their business.
I suspect that's exactly what Berkshire Hathaway does. It sells when companies are overvalued and buys when they are undervalued. Warren Buffet is the most successful investor in history. Carefully working out the value of companies is what allows his company to know when their stocks are undervalued or overvalued. One thing Buffet does is refrain from any calls if he cannot base a decision on sound analysis.
From the horse's mouth: