Retailers take far less than 30%. Consoles provide first-party QA, disc/cartridge manufacturing and distribution, bandwidth, and customer service among other services. Whole apps on the mobile stores also have similar services provided by the platform - testing (nowhere near as rigorous as consoles), discovery, bandwidth, customer service, etc. In both cases, a large cut can be reasonably argued for.

IAP is nothing more than moving money around, in an app the user has already discovered and downloaded, that will affect a user's account on the developer's servers. The service to the end user is indistinguishable to what is provided by any other payment gateway for ~3% (Stripe, Square, Paypal, etc.) Your card is charged and you have something new in the app.

The only reason I can think of for why IAP takes the same cut as whole apps is that most if not all apps would be "free" but open up to a screen that makes you pay for the app via IAP to take advantage of the reduced fee.

This could be mitigated by ToS restrictions preventing this exact situation, but there would still be a ton of gray area like "pro" versions of apps.

Opening up to third-party payment processors for IAP would create a vacuum in one of their highest margin and most consistent revenue sources so they won't be doing that willingly. Opening up to third-party stores would be more tolerable but any sufficiently large developer will move to their own store and do everything themselves and pocket the ~27.5% (if they are their own payment gateway, interchange fees are ~2.5%)

It's an interesting situation because the platforms want to be paid for all the services I listed above, but in Epic's case they already have the infrastructure to handle everything on their own, and they offer a fully-featured game for free, with the only source of revenue being a conversion of actual money to V-Bucks.

There is no place where the platform can provide a service that Epic would get any value from, but they are imposing a 30% fee in the only place they can, payment processing.

Retailers don't get 30%. Not even close. Try 0.5% or something like that. As for MS, their cut on the MS app store is 5%. 30% is just really really steep, and I think consumers would win if that got reduced.

Retail is not the place to compare markup. The lowest markup I saw recommended was 10%. Average was 20-30% and big box was at least 40%. There is no guaranteed win for consumers at all as prices are set what the market will bear.

I strongly doubt that, I’d bet prices would remain the same and Epic would pocket more

Part of the original thing was Epic offering a discount of 20% on V-Bucks if they processed the payment through Epic instead of Apple.

The end user got a nice discount and Epic still pockets more because interchange fees are ~2.5% and not 30%.

The Epic Games Store had a similar strategy, cut the fee for devs and incentivize end users to move onto their platform (weekly free games). They still make a boatload of money even though it's not as much as Valve's money printer.

In general I see this as a great thing for devs (indie in particular) if it triggers more competition to bring platform fees down across the board.

Epic isn't being overtly greedy with end users (yet)

I don’t know about that. I could imagine it going both ways. But even if Epic pockets more, there might be other apps which pass on the savings. And if not, well at least you can now subscribe to Spotify and Netflix directly on device.