The current Australia Post MyPost Business postage costs guide can be found at https://auspost.com.au/content/dam/auspost_corp/media/documents/mypost-business-postage-rates-guide.pdf

You can confirm your Send and Save tier on this page:

https://auspost.com.au/mypost-business/dashboard#/sendsave

Note that Send and Save tiers are based on a rolling 8 week period of label bookings.