Personally not really. There's a lot of choice in the industry these days so if you want/find a better deal then grab it. Move elsewhere and then just sign back up to Optus as a "new" customer if you really want to.
FWIW I think Optus is pretty good at trying to attract new and keep old customers. They generally open most plans to "New and Recontracting" customers. I tend to contract for 12 months. Then sit on that on a month to month basis. After a few months there's a flash sale which I am free to grab for another 12 months.
Not sure what the postcode conspiracy theory is? Either wealthy suburbs get super cheap deals (which is strange as Optus wants to maximise revenue everywhere) or its poor subburbs getting cheap deals (which seems nice?)