I can understand your irritation, but as I see it, it is not really a break in Apple's policy, it is just a very unfortunate and misleading naming of two very different products. I suggest to use the feedback form and write your post above to the developer team. This way, they will know about the problem. Use the form below:
Apple - GarageBand iLife - Feedback
When I buy a product in one device, I don't expect to have to pay for the same product in another device or computer (especially when they have exactly the same name!)
Just a few notes on this: You can use GarageBand iOS on many different devices, as long as they are able to execute the program. My GarageBand iOS is running on an iPod Touch, an iPhone 5s, an iPad 3, with only one purchase. All devices are able to run the iOS operating system and have processors, that can execute the code.
The same goes for GarageBand iLife. It will run on any Mac with an Intel processor, that can run a reasonably new version of MacOS X.
Have you noticed, that both GarageBands do really not have much more in common than the name? The iOS version for mobile devices is mainly a program to play and perform music using the iPad sceen , e.g as a musical touch instrument - as a guitar or keyboard, and you can jam along. The Mac version is better for arranging and mixing music or editing tracks and adding effects, but it does not support playing music very well. You need real instruments.
Regards
Léonie