I originally bought an iPad just for music stuff, but a lot of the time I'm hooking it up to an external audio interface for better quality IO and midi. I think that iOS' support for USB Audio and USB Midi devices is also a large part of what helped it build an ecosystem of decent music making apps.

I agree that not having a headphone jack combined with the unacceptable latency of bluetooth makes it unusable for on-the-go music making.

As for pricing, I think that won't change on Android. Music making is a niche market, and these apps are not cheap to develop.