Wrong.
Approach your local certifier and have a chat - they will quote you for the work and will probably recommend a local drafty to do the drawings as well - drafting and certifying a lean to should be $1 - 2k max. depending on the level of info you can give them including existing plans etc.
You will need to get plans drawn which don't have to be too detailed, but do have to nominate section sizes and tie down details etc., the certifier will then issue a building approval with conditions attached and you go ahead and build the thing - assuming you can and understand building/plumbing regs. The certifier will need to do inspections of the footings prior to pouring and of the finished structure. Job done.
It has always been like this (even when council controlled it), and it was never going to cost $1500 to do legally.