It's okay, if you're a AAA company with something like like 25-50m in sales, y9u get a tax cut to 20%

When you put it that way, the model makes so much more sense to matching how the US operates.

At least they're funding a lot of useful open source development with that money pile.

In a sense it's worse than that - when the mega-publishers started leaving Steam in favor of their own stores with better margins, Valve conceded by introducing a tiered system where their cut drops to 25% after $10M in sales and again to 20% after $50M in sales. It's deliberately structured to give a discount to the mega-corps which least need it (EA, Ubisoft, etc) while ensuring that indies with no leverage over Valve mostly remain on the 30% bracket.

30% may be a lot but you get more than a store page;

- anticheat

- voice chat, friend list, ...

- matchmaking

- marketplace for mods, maps, skins, ...

- clips and videos

- forums/ discussion board

- cloud saves

- rankings

An indie would have to implement and host those by itself or rely on third party services.

https://partner.steamgames.com/doc/features/

The problem is the margins are so high these digital storefront cuts almost become arbitrary. So to try and come up with a somewhat objective measure... 30% is too much based on their own historical pricing.

Steam was taking 30% when they did heavy curation and hand picked every game. At that point being on Steam was probably as valuable as a traditional publisher distribution wise because just being on Steam assured some level of quality.

Greenlight was the start of the decline in that value, and then with Steam Direct its just officially insane that they're still pricing their cut at the same rates they did at launch.

The value adds you listed also got much easier to build over time and got commoditized. EGS offers most of that for free for example, sans gambling enabling marketplaces.

Don't forget about their REAL expenses: credit processing fees and chargebacks.

Those are not even remotely close to 30%. If the cut was based on real expenses for services provided you'd see it change over time. That it's been stuck ack 30% for so long shows that there is only one reason for such a high cut: because they can get away with it.

Most games don’t have or need that functionality. Charging 30% because you could use that stuff if only you put in the development time is pretty rich thinking.

For example the Forums feature is seen as a plague, many of the forums on Steam are filled with neo nazi content and spam.