Oh.my.god.this.is.so.cool!!!! I can’t seem to find out how much it costs, though I could imagine it’s insane. Here’s the info from the designers website:

“With Jonas Samson’s high-tech light-emitting wallpaper it’s possible to use a two-dimentional flat surface as light source instead of a 3D object.
As long as the wallpaper is turned ‘off’, it is indistinguishable as a source of light. Instead, it is just what it appears to be: wallpaper.”

What a… BRIGHT idea!
(Okay, sorry. I couldn’t help myself!)