laravel sum column values

Sometime for such queries you need to disable the strict check
 So inside config/database.php and inside mysql, 
 Set 'strict' => false,

->select('user_id', DB::raw('SUM(points) as total_points'))

Product::where('id',$id)->sum('quantity');

Auth::user()->products->sum('price');
// And on your App/User.php you need someting like this:
public function products(){
  return Products::where('id_buyer', Auth::user()->id)->get();
}