Which even halfway credible app developer would sell you that info? You know that’s illegal right? You might get some stupid indie developer to do this but no chance for anything even half big.
But if you can get actually get this data, maybe try to do this on yourself and write a blogpost about it. I highly doubt you’ll be able to.
I've never made an iOS app and don't have plans to. But my assumption is ~every >= medium-sized iOS app would be monetised by selling data to aggregators.
Even if that was the case - which it isn't - the aggregator data isn't keyed by the user in question. That is highly illegal pretty much everywhere and would get you in a lot of trouble. You can't "just" find out which apps an arbitrary person has installed on their phone. That's not how it works.
My understanding is it's common practice. E.g. How Shady Companies Guess Your Religion, Sexual Orientation, and Mental Health And sell that data to the highest bidder. https://slate.com/technology/2023/04/data-broker-inference-p...
Most app publishers are halfway credible at best, so it's not much of a problem. Even the halfway credible ones often use SDKs that do this.
Ok but if the SDKs do this they use it themselves to serve ads and don’t sell the raw data, right?
Get your hands on a random selection of 10 iPhones and look at the apps installed. I suspect you’d be horrified. As an example - any parent who has installed a free game for their kids likely has all of this info, plus more via tied in logins.
That said, I agree with the rest of your point - you’re not going to go to a developer and offer them $100 for this data on a person (and if you could, you’d still need to tell them which person, which if you could do you could just get the data yourself)