Thankfully the Mac did not evolve this way
The in-app purchase was already starting to get crazy, now it is going to be nuts.
Imagine if the Mac was all in-app purchase. Click on "File -> Save" the program prompts you to click here to buy that feature for $4.00, want to print - that will be $4.00, ah you want access to the interweb - that will be $10.00!
In-app purchase should be restricted to content, not features. If Apple allows developers to use in-app purchases for features then the appstore will quickly become a nickel and dime fest for developers screwing people!