In this model ( just click the link to give a look at the enclosed valuation model ) I assumed the Revenues will decrese in the next couple of years; due to the ceasing of the Costco partnership. But I am confident that in the next years the management will be able to recoup the lost sale using the appropriate marketing mix.
Moreover, I kept the forecast very prudent, indeed I only forecasted an increase in sales averaging about 2%. The fair value is about 66 usd per share.
So today the stock should be lightly undervalued and would ensure a 6% -7% total return for the next several years but discounting a prudent and negative scenario. The total return should be way higher in case Amex is able to reach an organic growth of at least 5-6%.