I am just a mathematician, so my evaluation of economic models is restricted to the analysis of the equations. However, it seems to me that, in a perfect transaction, the selling price must be at least the value to each party.
Clearly, the value to the buyer must be greater than that to the seller. This is usually achieved by adding value. For example, a manufacturer purchases raw materials, or a wholesale merchant moves goods to where the buyers are.
That being said, I do not see where the added value is in the investment market, for a typical investor. The present value of future earnings and stock price are the same for both sellers. The only reason for the purchase is then an imagined increase in price beyond inflation, i.e. finding a bigger sucker.
Is the whole system just a house of cards?