Well, there is a 10% APR interest (current) on SBD. I don't think that justified the higher rates we've seen on the markets. In fact, I think 10% APR would indicate a lower trading value than approximately 1 USD / bitcoin.

It could be the case that traders speculated on Poloniex and Bittrex do not understand that this is a pegged currency and that the premium prices (at least in my opinion) are unjustified. If they do not realize / understand these mechanics, then the current market valuation makes sense.

I can't see any other reason for it otherwise. Naturally, people will want to move out of SBD to pay for bills, lock in gains, etc. With the total amount of SBD that is created per day, I would expect that these prices should reach parity much closer.

However, it is important to note that there is no arbitrage opportunity, or nearly none, in buying sbd or steem off an external market, selling on the internal exchange for the other token, and then selling the new token on the external exchange.