Re: Nxt :: descendant of Bitcoin - Updated Information
It's normal you can fulfull trades at any price you like.
No, it is normal when buy order is processed from the best ask price up till it is all fulfilled 
Something similar happened with someone in China buying LTC at 2436RMB, with the actual price at 236RMB.
http://www.reddit.com/r/litecoin/comments/1s5op0/someone_in_china_bought_litecoin_for_2346_yuan/