Given the BTC/BTC2X futures at 0.2 BTC2X for 1 BTC, a price drop of 20% is logic. A drop of 30% is understandable, if we assume that bitcoin price is currently overrated.
As it's not a straightforward fork as BCH was, I'm not sure I'd put too much faith in any futures prices. If you did it right you were guaranteed to get your BCH.
S2X's intention is to make your BTC useless. If people couldn't be bothered to claim their BCH, they're really going to struggle to safeguard both of their claims on the chains on their own.
It's very unlikely there'll be two chains beyond a couple of weeks so there's no point in pricing the both of them.