"But Apple needs to fund the App Store. XCode, payment processing, reviewers, it all costs money". Yes, very little in comparison. Apple made $50 billion in revenue from the App Store in 2019. $50 BILLION. The data centers costs to serve up this are miniscule in comparison. Apple could build 50 datacenters PER YEAR EVERY YEAR for that revenue. Reviewers? A staff of 10,000 fulltime reviewers paid $200k per year would…
Apples audited financials tell us gross margins on services is 68%, and $9B of those services are from an annual payment from Google for search placement in Safari with a gross margin approaching 100%. So you can make up whatever numbers you want given your limited understanding of what services the App Store provides, but App Store gross margins are clearly likely to be in the 50-65% range, making its break even somewhere between 10-15% of developer revenues.
And lastly, gross margins aren’t net margins. Apple still has to pay for marketing, sales, admin, support, etc out of iPhone gross margins, and the App Store still needs to contribute to some if these as well.