The financial markets would value Laffer Shares in the same way that they value all other equity shares, which is based upon the presentvalueof expected futurecashflows.
This is the same criterion used by the actuary of Social Security to compute the ultimate measure of the long-term financial condition of Social Security and used by private lenders in determining whether the purpose to which a prospective loan is put will increase the presentvalueof a company's futurecashflows by more than the amount of the loan.