We've only had a small number of Android users purchase the ad-free version of our game whereas we've had quite a few (about 10x) iOS users buy it.
It's only our first month, but those ratios seem to hold true for many other games. We've made back our developer fee already and should recover the cost of the Mac I had to buy in the next month.
I really didn't like having to pay for those things, but for us it wasn't an option to not support both platforms.
All that said, we did release on Google Play quite a few weeks earlier. That gave us a nice chance to work out some unforeseen bugs before releasing on iOS. So there's nothing wrong with making the decision to release on iOS much later. AppGameKit makes it super easy to work on both platforms. I only have maybe 3 different chunks of code that are dependent on the device type.
Hope that info helps.