sum row data and get all data eloquent laravel

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

$balance = DB::table('data')->where('user_id' '=' $id)->sum('balance');

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();
}