Yes, normally there is an official Chart like every index that is traded at the Wallstreet. I dont know where bittrex get their numbers but they gain much profit at every SBD that they steal this way from their users, 0,002 btc per SBD...

... you should always check the numbers before trading anything, especially the fees.

I never seen such a chart manipulation. Whilst poloniex shut down the SBD wallets bittrex is a kind of monopolist but normally companies get over the fee and arent manipulating the chart.