I am happy using my $229 kindle hdx that is just as high quality and a fraction of the price.
HAHAHAHAHA!
Seriously?
I have a Kindle Fire HDX - and given the price you quote, you are talking about the 16GB WiFi 7" one. Which is only fair to compare to the $479 16GB iPad Air (since everyone is price-matching Walmart now).
I love the HDX - great little screen, solid performance, excellent sound, and great immersion in the Amazon ecosystem I am already heavily invested into.
But ... and this is a BIG but ... EVERY major app is better on iOS. Facebook, Wordpress, on and on. iOS word processing & spreadsheets tower over what you can use on your Kindle. Games? Absolutely no comparison. It is an iOS first world for gaming. And music making - if that matters to you, which it does for me - again, Android isn't even in the game.
And quality? Really? Seriously? Again, the HDX is nice and is definitely better than the Nexus 7 in terms of build, but there just isn't a serious argument that they are equal.
Keep your HDX - I will certainly be keeping mine - but let's not pretend that these two things are equal.
I mean, heck ... the Kindle Fire / Nexus 7 screen is very small (and wrong aspect ratio) compared to the current iPad Mini, let alone the new Air.