SBD are trading at more than $7.50. BitShares bitUSD should be worth at least twice that, since they actually do what they're supposed to do...
The BitShares market pegged asset system has been very effective. I don't know why Steem only copied half of it for SBD. There's a proposal to fix this on Steem using the BitShares design here: https://github.com/steemit/steem/issues/1839