Good quality wallpaper can range anywhere from $1.50 a square foot ($50/roll) upwards to $14 a square foot ($500/roll).  Labor to install wallpaper can range as well.  The wallpapers level of difficultly to hang, the type of glue required, trimming seems, and if the installer must rent scaffolding to install the paper. 

Clients really want to get a ballpark for wallpaper, so here it goes...  

For a 12 Ft. wide by 8 Ft. high wall, with no windows and doors and a small pattern repeat, the combined wallpaper and labor price would range anywhere from $360 to $2500.  

Of course, the previous example is just a general estimate. Only after i visit the space, measure, and finalize wallpaper would Nook be able to give a firm estimate for the space.