Market capitalization = number of shares outstanding * share's current market price
Let me remind you one more thing you've probably forgotten. The number of shares outstanding is an objective quantity, and the current market price is an intersubjective quantity (i.e. a non-objective quantity, which is not entirely subjective because it is shared by different subjects).
Mathematics teaches us that Pi and e are irrational and transcendental numbers, but no one knows whether Pi*e is irrational or transcendental. Similarly, no one knows whether the product of objective and intersubjective quantities is objective quantity. In short, people may believe that market capitalization is something real, but they do so at their own peril.