Having been the TM for this tour several times and for the Travelsphere one, I know that guests on JY have found it good value for money.
Australia is more expensive than people expect: eating out can be costly, so to have breakfasts and several dinners and a couple of lunches included is useful to the budget, but not just that it is part of the JY/social experience.
Breakfasts in the hotels are very good: continental and cooked with lots to choose from.
Dinners: Sounds of Silence, a very special experience and is a sell-out; Tramcar in Melbourne, magical, also very popular.
People usually have to book both of these several months in advance.
They are all-inclusive: food and drinks - alcoholic and soft drink options.
Another point to bear in mind is that single supplements don't guarantee a "twin room for single occupancy", quite often it can be a single room. With JY you are guaranteed the twin room.
So, depending on your budget and on what you want from the holiday, hopefully this info will help with the decision-making?
Australia is a remarkable country, with so much to see and experience, so however you go and whoever you go with it is fabulous.