Destiny 2 on PC Buy Online from Battlenet Standard AU $58.46/Game + Expansion AU $97.46/Deluxe AU $104.96
Destiny 2 purchased direct through Battle.net. Cheapest I've seen it, and I've not seen it advertised in the Black Friday store sales for EB, JB, HN or elsewhere.
Grab it from the website link above, or through the Battle.net launcher if you already have it installed for Blizzard games.
Save up to 35% on Destiny 2 – Limited Time Offer
Digital Deluxe Edition
$104.96 usually $139.95
Game + Expansion Pass Bundle
$97.46 usually $129.95
$58.46 usually $89.95