There's a realistic limit on how long a glass-lined tank will last. Some of this is how concentiously it is manufacturered, some is luck of the draw, some is the local water quality, and some is just a gamble. The warranty can be extended for a price, but it is just an insurance policy - it doesn't buy you a better tank. With some, after you pay the 'upgrade', all they do is install a different sticker on the thing.
A larger or more anodes, a quality drain valve are part of the difference (not all that much at a manufacturing level cost, but at retail), and possibly a more reliable gas valve. Some of it is also the design - read some of the horror stories on the Whirlpool WH here (and elsewhere). BW generally has not had those difficulties. BW typically doesn't sell direct to consumers, so the markup is whatever the plumber thinks is fair verses what you might pick up at a big box store where they have huge volumes of the things going out. Because BW caters to the pros, and pros generally won't tolerate profit losing callbacks for defective or problematic products, these tend to be built better.