Hi! Please refer to this link https://www.mara.gov.au/using-an-agent/working-with-your-agent/agent-fees/
This gives you an idea of how much you may pay an agent to assist you with your visa. In this way you know if you are being ripped off. Knowledge is power.
Unfortunately, there are a lot out there who use our profession entirely for money making purposes. However, there are still those who are still in touch with their moral values so be very careful in choosing your agent.
If you are fees conscious which I can imagine you would be, maybe I could help? Feel free to visit my website www.visaconsort.com