The only way for Google to ship something like this at this price point is to eat a big chunk of the production costs and sell it at a loss.
The reason for this is, I think, kind of obvious: everyone needs a phone. Most people buying new phones opt for smartphones, and the cheapest smartphones are droids. They serve the market.
Tablets, however, are a luxury item. They're not a necessity like a phone, nor are they a productivity item in the same way a laptop is. The people who buy them are buying them as luxury/status items, and that means Apple. Just as those who buy phones for status buy iphones, so too do those who buy tablets buy ipads.
The only people who buy luxury phones and tablets, but opt for android, tend to be the technorati which is a much smaller market than Apple appeals to.
iPads replace laptops for many people which explodes your hypothesis. I've never purchased a laptop in my life due to expense but I did buy an ipad. New category =/= luxury.
Apple has won this category because (among other things) they were the first successful entrant, their software is more refined, their ecosystem is better and their distribution is leagues better.
Like a lot of people I'm working on the go all the time and as much as I like tablets for certain things I need a real laptop.
You're pivoting to a very circular definition of luxury here. A laptop is something that would have been very useful to me, as it turns out it always ended up one lower then other things on the budgetary priority. That doens't make it a luxury/status item as you said 3 up.
Ultimately there's a contradiction in your claim that a laptop in general is not a luxury/status good ("sign of affluence" - wiki) but a cheaper iPad, which often functions as a laptop substitute, somehow is.