Not as cheap as Myer was, but cheapest I've seen otherwise and they have just been reduced. They are also showing as arriving tomorrow for me in metro Melbourne.
Note that the RGB are not compatible with the RGB+W, so you can't put them in the same group. E.g. no good for a Christmas tree if using different set types. You can use them separately though.
RGB+W
If you're in/near Perth and a Costco member, you might prefer this deal if they're still available. They're not quite the same lights and probably can't be grouped with any of the other Twinkly lights, but should be good on their own.
David Jones has Twinkly on sale too for just a few more dollars per item and available in lots of stores still? if anyone wanted to have it for Christmas. They don't have the 600 Strings though but do have 400 and others most other items. They have the Festoon ones that Amazon doesn't have as well.
https://www.davidjones.com/search?q=twinkly
Example. Strings 400 LED RGB Smart String Lights $209.00 vs $203 at Amazon.