The expectation of a 10X (1000%) rise in the STEEM price over the next 5 years is not totally unreasonably given the very large market capitalizations of traditional social networking behemoths such as Facebook and Twitter.
Apples and oranges. You can't compare the market cap for a company (like facebook) to the market cap of a cryptocurrnecy like steem. It simply doesnt work.
And even if you could, you can't do it backwards (which is what youre trying to do) the market cap doesnt determine the value, the value determines the market cap. You can't just say "steem is better than facebook, so steem marketcap should be higher, so steem should be worth more as a currency"... well, you can. But you won't be making a ton of sense, imo.
The price of steem and steem power is going to be driven by supply and demand, not by some fantasty about parity with facebooks marketcap.