Some Earth Defense Force games are at their all time lowest prices.

Some of DLCs are also 50-60% off so make sure to check if you are interested in those.

EDF Iron Rain: https://store.steampowered.com/app/1039890/EARTH_DEFENSE_FOR...

EDF 5: https://store.steampowered.com/app/1007040/EARTH_DEFENSE_FOR...

EDF 4.1: Wingdiver The Shooter: $4.05 AUD: https://store.steampowered.com/app/574200/EARTH_DEFENSE_FORC...

Enjoy!