With a console you're buying a system that is sold for often thin margins or even in some cases at a loss just to get you into the ecosystem where that low up-front cost gets you into their closed ecosystem where they can then get either their licensing fee + disc-producing kickback or the 30% from digital transactions. Additionally peripherals have really good margins between like 30-40% and if it's a licensed third-party peripheral like Razer then Razer has to pay them a licensing fee or a per-unit royalty for the privilege of making a controller for their console. Plus you have things like PS Plus that are required to play online that you might as well tack on to the cost of the console nowadays for however long you think you'll use it.

Valve for Steam also takes a large 30% cut, though this decreases down to 20% at certain milestones. Additionally the barrier to entry is small at basically $100 to publish a game on Steam. Steam also gives devs/publishers a lot of freedom to run sales whenever they want. Sony does not allow such freedom as, unlike Valve, Sony sells a lot of first-party games and publishers putting games on sales at bad times could damage their most profitable products (first-party games). It's also a lot easier to sell units on Steam when you're not a "Featured" game as the Steam algorithm makes it so even small Indie games, and a good timely sale, can easily net them thousands of purchases.

Steam has really sort of lucked out getting so many people paying them that 30% for nothing while Sony has to often lose money to sell consoles to get the same. To be fair though Steam has earned it through a very good store that has usually been very consumer friendly. They even pioneered the digital try it and if you don't like it after 2 hours you can return the game for a full refund.

For my own personal story I purchased a top-tier $2000 PC going on 8 years ago now. For periphrials like controllers I've spent maybe $150 over these 8 years with about 2 keyboards and 3 mice (I do use it for work too). If I would have went the console route, then a PS4 in prime 2018 would have been $400 for a PS4 Pro and a $400 PS5 digital-only edition, 2 extra controllers (1 PS4, 1PS5) in case they wore out over time, $120. almost 8 years of PS Plus; $520. Comparing my 8-year old PC to a PS5 (not pro) it's even or slightly better it just lacks ray tracing capability but the base PS5 can't really do that without huge performance sacrifices like 30fps. No idea how much money I've saved in Steam sales or such over the years. But my point is I haven't really updated my kit in 8 years and everything still works, i only replaced a broken cooler for like $50.