This hasn't been much cheaper in a long time (I picked one up for $59 several months back from the EB deal), and it is currently not available on Amazon except through 3rd party sellers.
This deal: https://www.ozbargain.com.au/node/572934 is cheaper if you want more than one bulb, but if you're only after a single, and you want it now, the Big B has you covered.
They have the screw fitting bulb for $67.70, which is also good, but it is unusual to see the bayonet fitting as cheapest.
Note that this is the latest bluetooth-enabled bulb, not old stock of the previous version.
There are a few other Hue items that they have matched the Amazon price on, such as the motion sensor ($39 if you missed the now-expired Amazon deal), and the outdoor motion sensor ($71), other items are full price.