Most applications of Metcalfe's Law use a coefficient to determine the value of a network. From this Wikipedia page, we can see the coefficient for Facebook is 5.7 X 10 ^ -9 based on a monthly active user count. Your calculation is correct if we assume the coefficient is 1. Which is very optimistic.
But, let's say that we that bound the valuation of Steem to 10 cents per Steem with the current user base. This is a very pessimistic valuation btw. That makes the coefficient for Steem around .045. If we expand to 100,000 active users in the next year using Metcalfe's Law and add 9.5% inflation to your current Steem number, we get a lower bound for 2018 of $1.56. If we reach 200,000 users by this time next year, that number goes up to $6.34. And that is using Metcalfe's Law with a pessimistic lower bound. Things are bright if the network can stay healthy.
RE: The Price of Steem should currently be trading at $2.22 and here's why: