From a study commissioned by Apple, but independent in nature:

Originally offering approximately 500 apps for the iPhone and iPod touch, the App Store has grown to distribute millions of apps for the full suite of Apple devices (iPhone, iPad, Apple TV, Mac laptops and desktops, and Apple Watch) in 175 countries. Cumulative downloads are in the hundreds of billions.

And:

The goal of this study is to capture total billings and sales generated through app developers’ various monetization strategies. In other words, our purpose is to estimate total billings and sales facilitated by the Apple App Store ecosystem. Our study accounts for billings generated through direct monetization via the App Store and sales generated through monetization outside the App Store.

With that last point in mind:

We estimate that the Apple App Store ecosystem facilitated more than $500 billion in billings and sales worldwide in 2019. More than 85% of that accrues solely to third parties.

Jaw dropping numbers, especially considering how lean times got before Steve Jobs’ return and the rollout of the colorful iMac, the iPod, iPhone, iPad, Apple Watch, AirPods, etc.

Apple has really blossomed.