I'm all about pricing for value without regulation. But did the App Store lose half of it's value to developers when Apple decided to slash fees from 30% to 15%

I'm all about pricing for value without regulation. But did the App Store lose half of it's value to developers when Apple decided to slash fees from 30% to 15% (for smaller companies)? I don't think so. Did a competitor to the App Store appear to try and compete for lower fees? No. This is just the behaviour of a company that can change prices on a whim because they don't need to compete with other app stores after having established a large share in the market and controlling 100% of all third party app distribution.