Probably because monero is being listed at a new exchange, a china based exchange. Not only 50%, it's over a 100%.
I'm not surprised caused by the monero already listed on the chinese exchange site but i think that you can see a lot of thje coin already listed on the because the hype is not for the long time, and you can try to buy them again in the future with the cheap price. Monaco as a good example for that.