Ok I met the most lovely bloke about 8months ago getting my gas bottle refilled in noble park…fast forward to last weekend. Back in Australia and need gas - go same place and its only $15!!!! I pay $25 in Perth and cannot believe no-one knows about this shop.
Anyway look up Jacksons Road Service station Noble Park (kinda close to the freeway)
Google has pictures of the sign saying $15 - go there for cheap GAS and enjoy great company while you wait :)
(Seriously the guy is a deadset champ)
The places that actually refill are few and far between. Used to be one on Heatherton Road in Springvale South as well, cnr Hosken St. Not sure if they still do it, recall their prices were good too.