I said skill. That is something else then a good idea. The fact that you might know 100 developers does not mean that you know a representative sample of the entire developer community.
haha - you said "skills" - ok, the developers I know have skills. And my quote of 1% of all apps making money is NOT based on the 100 developers I know from my network. It's based on different reports that examined the market. The 100 devs I know can be seen as a kind of proof (or not) ... just as you like.
And you said
If you have a good idea and can implement it, then luck and marketing budget do not need to be factors.
The only thing i would like to clarify here is that one of both IS needed (minimum). Either luck OR marketing money. Even IF a developer has all the skills and good ideas in the world.
And did you know that even the definition of "a good idea" in that environment is based on a lucky moment to get the right thing at the right time? It's not easy. It's NOT a fact that you make money selling your app because you just are a skilled iOS developer with a good idea.
I bet that 80%-90% of all apps don't bring in the development and marketing costs. Apps will convert more and more to must-haves for companies (like web pages) and/or gaming apps with a team of people that figure out how to get the users addicted and find the hot spot where to earn money by consumable in-app purchases.
There are niches – but they are really hard to find.