Let me make this super clear; Apple adds a 30% tax onto everything in the App Store. This is to cover the cost of their reviewal process and costs to run the App Store. 30% is extremely high and more than enough to cover these costs. Apple does not provide servers for Spotify. Apple could literally charge 1% and still make a profit.
When you buy an app, you are always paying an extra 30% because of Apple.
You really have no idea what you are talking about.
First, 30% is deducted from the price you set. Whether you set the price of the app to 99 cents, $1.29, $10, $99 (or whatever price you come up with) Apple takes 30% from that price. They do not tack on an additional 30% to that price, nor is it the purchaser's responsibility to cover that 30%. You don't get billed by the developer and then Apple charges you an extra 30%, lol. They take their cut from the developer directly. Some developers therefore add an extra cost, to cover that 30% ... which is what Spotify did. But it's not Apple charging you that extra 30%, Spotify itself is charging that extra 30% to cover the cut Apple takes from them, not you.
Let's put it in other terms.
A store owner sells fruit ($1.10). The store owner must buy the fruit ($0.10), and sell it with an additional cost in order to turn a profit ($1.00). You can easily say, that if the store owner wasn't being charged ($0.10) ... then you would be paying less ($1.00). And because the store owner is being charged, and passing on that charge ($0.10) to you ... the supplier is the one that's indirectly charging you ($0.10). That's how your mind creates the situation, but you're not realizing this structure exists in every buying situation unless the person is selling at a loss (thus selling for less than their purchase price). However, maybe your logic is that Apple's 30% is unreasonable. So let's go to your second delusion.
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Second, the developer / company is responsible for the data transmissions necessary to use the app, but the developer does not distribute the app itself. Therefore, every user that downloads the app is doing so from an Apple server. Although not everyone will download Spotify's update, at least 50% of their 60 million users will do so (or 50% of whatever their number of users that are on iOS devices would be Apple's minimum burden). That is a very large burden, and it does not even factor in the users with multiple iOS devices. There are many burdens that Spotify incurs aside the staff burden required to review the app, and there are many benefits Spotify gains (such as exposure, accessibility, etc).
You've painted this fantasy in your mind that has no grip on the reality of the situation. I wouldn't be surprised if you think Spotify teleports the app to your phone. But in your imaginary situation of Spotify distributing the app to users directly, if Apple's servers aren't at the very least checking the fingerprint of an app before it installs ... then the developer would be able to change the codebase at will. And there are a lot of developers that would do something malicious if they had such freedom (jailbreaking would be unnecessary, because exploits would be easy). An alternative approach to exclude Apple's servers might be, every iOS device could have an internal digital fingerprint / checksum database to verify the downloaded app against. This means the device needs to have the fingerprint of the app before the app is installed (if it's not accessing a server to grab the fingerprint). Considering that iOS updates are less frequent than new apps are created, how does this internal fingerprint database get updated without using Apple's servers? lol. And if the devices are only grabbing the new fingerprints from Apple's servers, how many new apps and app updates are pushed to Apple's servers every hour? So how many iOS devices would be hammering Apple's servers to get those fingerprint updates every hour? Okay, let's say that somehow magically the fingerprint database inside each phone gets updated without ever accessing Apple's servers ... what is to stop me from hacking the codebase in a manner that produces the exact same fingerprint since I'm distributing the app directly? I assure you, it can be done.
The only secure situation is if Apple stores the verified codebase themselves, and distributes it themselves. Hence Apple handles the distribution, and the developer pays Apple for that distribution. Then the developer handles the data transmissions required to use the App themselves, that is, if the app does not internally do it (for example you can create an app which accesses other's servers, but never your own, which in that case you'll have no direct server costs of your own). Let's say, of the 60 million Spotify users, only half of them are iOS users. That still means, Apple must distribute to 15 million users within a short amount of space, and few more million users that delay updating. What is the fair price for that if 30% is too much? What about the other burdens Spotify incurs? Even accessing Spotify's app page uses Apple's server resources. So what about the people that check the app just to see the reviews but they don't even download the app itself, because they instead liked how Tidal looked?
Apple should just say "we got this, don't even worry about it!" *waves to Spotify to keep their money in their pocket that they acquired from the App store, as if covering the bill at a restaurant* "We've got this."
lol.
Thank you for amusing me.