I think one of the main reasons it's so hard for new developers to make money is that -- as has been said so often -- discovery is broken on the App Store. The "new" category basically doesn't exist anymore, and even if it did there are a ton of new apps being released _daily_.

For everyone's complaints about Apple's stringent review process, there's a ton of crapware on there, which makes customers really hesitant to buy.

In [some] ways you're better off charging _more_ money and targeting a highly specific user base. Then you at least have a good shot at reaching the top-grossing lists in niche categories and gaining visibility.

Edit: to be clear, there's a lot of different types of apps and the free or IAP route can be the right choice. But, IMO you need something that has mass appeal if you're going to rely on converting small percentages of free users to paid users.