what you need to understand is that google and apple make their money in very different ways. Google can afford to sell their products for little to no (or even negative) profit...they make all their money off selling ads through their services. The more they know about you and the more you use their service, the more money they make.
Apple's services, on the other hand, exist to support their hardware, which is where their money comes from. For the most part, they don't sell your data, or present ads to you (though iAds does do this, most of that money goes to developers, not apple), and they don't make money from you using their services. They make money from you buying their hardware.
Now, I'm not really one to be bothered by google selling my information...things have to be paid for somehow, and I'm not self centered enough to feel I'm entitled to google services free AND ad-free. But it bothers some. And iOS is seen by many as a superior product, not necessarily in features, but in usability and stability, and that's worth the money to some.
Also, don't forget that a majority of people buy their phones on contract, so its $200 either way. Were I to buy off contract, it'd be a GNex, hands down, simply because of the price.
And, it's worth mentioning that your comment about the tablets doesn't hold up like the phone does...the nexus tablet isn't in the same class as the iPad. It just isn't. There's no argument for that
