Cube Scape seat creaking
It's unlikely that the issue is the seat itself.

In 99 cases out of 100, the issue is that seat clamp at the top of the post that holds the saddle rails is loose, or wearing.  Usually loose. 

Grab your set of allen keys, find the 5mm or 6mm which will fit the 2 bolt there, and tighten them up to about 10-12 Nm. If it still creaks, consider replacing the post, but it shouldn't come to that.