Stellaris is currently $1 (AU$1.25) over at Humble Bundle, which is only slightly more expensive than free. That's for the base game, which fared well in our review back in 2017, but you can also pick up a handful of its expansions if you pay a bit more.
If you pay $10 (AU$13) you'll get the Utopia and Leviathans expansions alongside the Plantoids Species Pack. If you fork out $15 (AU$18.79) you'll get an additional four expansions: Synthetic Dawn, Apocalypse, Megacorp and Ancient Relics.
If you're yet to dip into the outer space grand strategy game, it's well worth a shot: it's among the best space games on PC and the best 4X games. The Utopia expansion was Stellaris' first, but brought "Stellaris closer to its original promise with a stellar rework of internal politics and new endgame goals," according to our review of it.
The bundle is available for the next fortnight, with purchases supporting the One Warm Coat charity, as well as another charity of your choice.