If they can make an iPhone and iPad retina, why not iPad mini?

a lot of people on these forums are saying it's near impossible and would be an "engineering feat" to make a retina iPad mini.

I disagree - the retina iPhone is stupidly light, has a good battery life, and is thin. So why can't they just make everything bigger in it. The only issue I see here is price.

Is there something that I Am missing?