Simple explanation: Yobit has not updated the wallet for months so GRE can't be taken on or off.  The price on Coinmarketcap is based in part on this price.

Complex explanation: This appears to be part of Yobit's business model from what I have seen.  Many coins are in the same boat - last I checked.  Purchasing coins there often results in people dumping them at a low rate after they find out that they can't move them off the exchange.  (I've personally done this but have long ago stopped trading on this exchange) Pumping a coin is really easy if you know there is a limited amount of them on the exchange and no new coins are coming in.  If you are one of the few with GRE on Yobit it might be fairly lucrative if you play your cards right.  The ethics of this is highly questionable imho, lol.