hey SS. I dont actually live in docklands and you seem to know the place well. Do you happen to know what that parking lot cost that is on the main streets, then you walk past hungry Jacks (only little one) then up the stairs past southern cross over the train tracks and to the Dome. That is pretty cheap parking by memory.
I don't live their either. But the ones you are talking about are scattered throught the city and most are Wilson parking. So a little googling got me this;
http://www.wilsonparking.com.au/go/regions/melbourne-cbd
Click on Southern Cross Station and I think that's the one you are talking about near the HJ's. Otherwise as you can see on the map there is a huge amount around the place that are close enough for you to walk.
btw I'm going to create a thread with a map etc. and I'll link this thread to it, or maybe a mod can merge the threads for me. (gimmie about 5mins to make map and get all the details etc.)