Each agency, and often each agent charges a different fee based on the services they offer and their own personal burden rate.
Statements to the contrary are a breach of the Sherman Anti-Trust Act.
Being successful in real estate requires a huge commitment of time and money and again unfortunately most agents consider real estate to be a low overhead business and end up with incomes to match.
I've attached a link below that you may find interesting on how to find a great Realtor.
I wish you all the best.