With JB Hi-Fi's excellent offer jumping up to $69 now that the game is released, this might be a great way to grab a copy -- especially if you've got any spare credit lying around.
Update: As people have pointed out below, Green Man Gaming are charging a different price for Australians -- but they don't charge in Australian prices. It's in US. To get the cheapest price, you'll need to use a VPN so you can get the $48 offer available -- and then you can apply the 20% discount to that.
Thanks to morkai and everyone in the comments. The original story is contained in full below.
It's all thanks to a 20% voucher from Green Man Gaming, which naturally you'll want to use to get 20% off Fallout 4. You can use the code in conjunction with the Season Pass as well, if you're insane enough to buy those things upfront, but otherwise this is a good way to get a digital version of Bethesda's sprawling RPG for a reasonable price without getting gouged on Steam directly.
Once you apply the SAVE20-NOVEMB-GAMING code at checkout, this is what you'll get:
I tried using the voucher in conjunction with GMG's deal on Star Wars: Battlefront, but it wouldn't let me insert the voucher. You can probably try this to get other games that are 20% off (Call of Duty: Black Ops 3 on PC, maybe) but for now the obvious deal is Fallout 4.