When it comes to relievers its best to get them at your price.
Gotta's point about throwing significant money at pens is correct. All you need to do is look at a guy like Fernando Rodney last year to show you how bi polar certain pen arms can be.
The guy has a 3.75 career ERA and last year it was 0.60 and he arguably had one of the best (if not the best) closer's season of all time.