Awesome Until They Do the Bait and Switch on You
Honestly, I'd gladly pay the same for this as I will for Infinity Blade 2 -- I think the gameplay is that good. Sure, it's just a shooter, but the concept is really cool, and the shooting and presentation are top-shelf. Unfortunately, you can't redo missions you've already completed, so there's no way to grind out money in order to purchase the weapons and gear you'll need to take on the game's more brutal challenges.
That's truly a shame because CK Zombies does so much right. There are some neat story tidbits, and the environments and mission variety are entertaining in the extreme. The visuals are some of the best you'll see in a freemium iOS game, and the sound design is simply stellar.
In the end, though, the publisher refuses to let you enjoy the game. The asking price for in-game gold is outrageous, and there's no way to simply purchase the game from the App Store outright. What a waste of an otherwise excellent iOS zombie experience.