You are not making sense. The value of the shares doesn't matter, what matters is capital gain. And Buffet is not responsible for their tax burden, he is only responsible for ensuring that he maximise the captital gain (the shares will go up in value). Given whatever level of capital gain the shareholders are still better off with a higher capital again, i.e. even if the tax rate rise, if the company is growing, it's worth more to shareholders, the share value will rise.