As @flash74 said, you'll need a prescription.
Testosterone is on the restricted medicines list in Victoria, and probably elsewhere in Australia, so the doctor has to hand write the details in, as well as print them, and can only issue you repeats to cover up to six months at a time.
You will pay full price for the items. Flash's gels cost him $100, whilst the subsidised cost would be $38. I don't know how much Nebido is.
Injectible testosterone is cheaper, something like $30, which falls under the PBS threshold, so if you're a cheapskate who can cope with needles, there'd be no savings if prescribed by an endocrinologist.