When I first moved to Melbourne, a friend told me about 'Lentil as Anything'. It is a not-for-profit community organisation where you pay what you think the meal is worth. I went for a meal at the St Kilda 'Lentil as Anything' to check it out! The restaurant is run by volunteers and it is a bit of an alternative/hippy restaurant with a Moroccan theme.
I really liked it as it was something different and the volunteers were lovely and have been very attentive every time I have visited. I can take a seat anywhere I like and they will often bring me out a menu and a glass of water. The food is really good and suitable for both vegetarians and vegans, and they also serve food that is gluten free.
There are no set prices. They have a box on the counter and you put your donations into that. There is more information on their website.