To reach 10 $ I do not think it necessary to create a community of 2,500,000 users and I would apply the Law of Metcalf, we use the metaphor of the phone, if there is only one, as such has no economic value. According to Metcalf's Law, if there are two the network of telephones is multiplied squared. The economic value of the network increases from zero to two squared, or to four. Adds a phone to the network and the value of the network will be nine. In other words, the economic value of a network grows exponentially, not arithmetically.
Excuse my English, my native language is Spanish.
Greetings from Venezuela
Great point used! Law of Metcalf is the reason for the tremendous success for most of the big organisations . Like Google, FB, and mostly anything that connects 2 or more points of interest.