The author made a disingenuous comparison. Dungeon Keeper didn't cost $5 when it was released many years ago. It costed $39.95. And there was not trial play ahead of time. Is he willing to pay for $49.95 (adjusted for inflation) for the iPad version before even playing it?

The in-app purchase got to this way because of gamer purchase behaviors. If the majority of the gamers are willing to pay upfront, you won't see in-app purchase. This is just like most people (at least in US) unwilling to pay the full price to buy the phone upfront but rather to pay for it with smaller monthly charges via the long term contract.

Gamers change their purchase behaviors and in-app purchases will go away.