I think Coinmarketcap is making an Average of the markets that have SBD to give out the price of it. You can check on SBD's page on Coinmarketcap the Market tab and see all the markets and their SBD price. One of those markets is HITBTC where SBD got even to 70$ these days. HITBTC created that boost for the SBD price.
Check here: https://coinmarketcap.com/currencies/steem-dollars/#markets