Use single quotes. I cannot stress this enough. Also $ is the string-end metacharacter. I doubt you want this when splitting.
You may want to use something more like preg_match_all for your matching:
$matches = array();
preg_match_all('#(.*?)\s-\s(\d{1,2})\s*#', $item->title, $matches);
var_dump($matches);
Produces:
array(3) {
  [0]=>
  array(3) {
    [0]=>
    string(17) "a few words - 25 "
    [1]=>
    string(22) "some more - words - 7 "
    [2]=>
    string(29) "another - set of - words - 13"
  }
  [1]=>
  array(3) {
    [0]=>
    string(11) "a few words"
    [1]=>
    string(17) "some more - words"
    [2]=>
    string(24) "another - set of - words"
  }
  [2]=>
  array(3) {
    [0]=>
    string(2) "25"
    [1]=>
    string(1) "7"
    [2]=>
    string(2) "13"
  }
}
Think you can glean the information you need out of that structure?