Wow, still very impressive and profits are only slightly down.
I'm surprised people still buy that many Ipads. All of their Ipad models have been so similar.

I'd have to disagree with that.

iPad 2 had twice the CPU speed, twice the memeory, and eight times the GPU speed while decreasing weight and dimensions. The design improvement was so shocking that Samsung actually retracted the Galaxy Tab 10.1 that they displayed at the Mobile World Congress in 2011 so they could make design improvements to match Apple's.

iPad 3 quadrupled the number of pixels and introduced near-perfect colour reproduction. As the screen is both the key input and output of tablet computers, an improvement of this magnitude is very important, especially for replicating the high-quality images and typography of print publications. Also doubled RAM, GPU performance and introduced LTE networking.

iPad 4 certainly was a minor release to tide things over. The only model that I'd agree fits your description. Still managed to double CPU and GPU performance.

iPad Mini offered identical technology to the iPad 2, but in a form factor with half the weight and volume. And make no mistake, weight and volume are key performance metrics for tablets. The less they weigh, the more use they'll see in different locations and situations.

iPad Air introduced 64-bit computing to tablets, roughly doubling performance yet again and cut weight and volume by 30%. That may not sound impressive, but let me tell you the difference is staggering when you hold it in your hands. Reviewers who had no interest in a full-size tablet have suddenly found themselves torn between the Air and the Mini.

iPad Mini with Retina took the Mini in one year from performing like a second gen iPad to performing like a fifth gen iPad. A three generation improvement in a single year. The Air perfroms marginally better, but the key decision for buyers now is how large they want their screen to be.

In three and a half years, the iPad has quadrupled pixel count and memory, reduced weight by over 50%, reduced size by 67%, benchmarks 25-33 times faster, and mantains a ten hour battery life.