The government has a recommended scale for notary fees. You can find this at www.notarynsw.org.au
There is a reason for these listed fees. These reflect the professional time costs of performing the various items.
Some notaries undercut these fees and opt to charge less. This might mean that they are choosing to make a loss on the real time needed to perform the task. Of concern however is when the notary rushes the task since they have ‘underquoted’. They might be short with a client, or not ask as many questions or just rush a job inviting inadvertent mistakes.
Personally I would be wary of using a notary who charges noticeably less than the recommended scale. I have had to fix notarial work of notaries who haven’t completed jobs with proper diligence and care.
Of course, the matter is up to you, but the recommended scale exists for a reason. And that reason is that it is a fair estimate of the charges.