Remove wallpaper or hang 1/4 in drywall over top?

[Gabriel G.]

So I am curious, a friend of mine and I are working on a flip and some of the rooms have wallpaper all around. One of the contractors we spoke to mentioned that it may be cheaper to just put drywall over top instead of removing the wallpaper. I would have imagined that removing the wallpaper would have been cheaper... @Ned Carey @Russell Brazil @J Scott Any thoughts? (Some pictures below)