Berkshire's MidAmerican Energy Holdings Co said on Wednesday it will buy NV Energy for $23.75 per share, a 23 percent premium to NV's Wednesday closing price. NV Energy shares rose to $23.90 in after-hours trading on Wednesday. It is not uncommon for shares in Buffett's target companies to trade slightly above the offer price, even where there are no competing bids and Buffett has said explicitly the offer is his best and final one.