The Witnesses are giving prices but the prices is far from stable (obviously, its pretty much guessing at this point lol).

Bittrex and Blocktrades, among others, will be trading HIVE once they finish their maintenance. At the moment, STEEM (and HIVE) are both under maintenance on the exchanges. That's normal for new coins/forks, hopefully it'll all be done within the next few hours if not today.

On hiveblocks, we can see the Witnesses current HIVE prices listed. Looks to me like they are assuming its inheriting STEEMs price until the exchanges come online and trading sets new prices.