You could always drive to a train station on the same line, and save the $20.
Would it be any faster, or much slower? Depends on how many drive and how many trains they run. It can take a long time to get out if lots drive, whilst the trains will be easy to get outbound with that amount of people going (especially as most will be coming from the city).
I'd probably do it if I was coming from woop-woop and wasn't scared of being rolled for my Nikes at Cambelltown. Unfortunately, I live in a civilised area. (Woosh! Cheap shot!)