Bear in mind that a lot of the cheaper Pharmaceuticals available anywhere in the world now are being counterfeited in China & India. These usually contain only a fraction of the active ingredient (-if any). This is especially true of struff bought over the 'net.
However you can save some money on what you need by:
1) Find a GP who will bulk- bill you for writing out your repeat prescriptions
2) Ask for Generic Brand medications.
3) Some medications are available at a discount from National Health Pharmacies. They charge a small annual membership fee. However, this 20% discount applies to almost every thing else they sell, as well (-including Vet supplies, which saves me about $200 a year!)
For people with conditions such as diabetes, you can join national organisations who buy in bulk and pass on the savings