That's a simple way of looking at the valuation of a company. However, this only presents a relative picture, but not a realistic reflection of the company’s future cash flow. It depends upon what P/E you are using and what you are actually earning per share is. In other words, the intrinsic value of the company is higher than the stock price; therefore, if you just add up the stock face-value, it will be undervalued.
We are just using historical data and really have no true access to the business prospects of the company. In other words, evaluation of stock requires addition information. You have to take a deeper look at the qualitative overview of the company. - If we could get more information and do a nice clean spreadsheet, we would be able to examine the current and future overall health of the company. The quality of the valuation is higher than just looking at the price earning method.
I have never owned or worked for a company that was publically held - dfhoggs may know more about the "actual" stock valuation. - Maybe he could give you a scenario using RRGI. - a quick lesson for all - he sounds a little smarter than I.