Game prices are about the same on console and PC
Steam has the obvious advantage here, and it comes down to them letting developers generate keys that can be activated on Steam. The "secret sauce" is that these keys can be generated and sold by the developers without giving any cut to Valve (the developers keep 100% of the profits).
This allows for things like Humble Bundles to exist. It lets sites like Fanatical or GreenManGaming work as outlets for developers to make a higher profit while selling the games for less (as
Zathalus
pointed out above). It's also created a healthy "second hand" market in the PC space. These keys aren't used, but are purchased by individuals on sale and held onto then sold for a slight markup later when the game isn't on sale. These things are all pretty unique in PC game pricing.
the official steam prices are the same as on console
If you're trying to save money on gaming, but artificially limiting your purchases to the official Steam store, you're getting exactly what you deserve. The fact that PC gaming isn't a walled garden (there's the Epic Games Store, GOG, Amazon, etc.) and there is customer choice is another reason why PC games are typically cheaper than you'd find on consoles.
If you're absolutely dead set on spending as little money as possible buying games, the Epic Games Store gives away a free game or two every week, and they've usually got a decent selection. This week is River City Girls. It's $0, and you get to keep it in your digital account forever. No subscription required. They've been doing this for years, and if you keep up with it (logging into their website, clicking the link every week to "buy" the free game), then you'll have about 600 games in your account at this point: stuff like GTA5, Plague Tale, Alien Isolation, Batman Arkham trilogy, all three Bioshock games, all the Borderlands games, Control, Death Stranding, Just Cause 4, Nioh Complete Collection, the newest Tomb Raider trilogy, The Calisto Protocol, Elder Scrolls Online, and Watch_Dogs, among hundreds more. All for zero cost.