The 30% cut was industry standard for digital distribution for years. Google, Apple, and numerous other players all took 30% as standard.
That being said, Steam hasn’t taken a flat 30% for years now - their standard agreement starts at 30%, decreases to 25% after the first $10m in sales, then decreases further to 20% after $50m.
Furthermore, Valve has done more in terms of providing services, APIs/libraries, and end-user features (all with no additional fee to the developers or consumers) than any other game storefront has. I’d say they more than justify their cut.
Everything you mentioned about the Tesla vehicle issues is largely inaccurate. It’s not your fault, because there’s been a ton of sensationalized stories and misinformation thrown out there about them. Full disclaimer: I do own a 2020 Tesla Model 3 and love it. It’s not a perfect vehicle by any means, but it’s a whole lot of car for what I paid, and it’s required almost no maintenance or attention from me over the past 4yrs beyond rotating and changing tires. I don’t like Elon Musk and think he’s a giant tool/lunatic in so many ways, but Tesla makes pretty damn solid cars despite him. I wish they’d get rid of him, though I bet he has a controlling/majority share unfortunately. I bought my Tesla before he became a huge raging asshole on public platforms, and that definitely contributes to hesitation at buying another in the future (though that’s several years out anyway).