Yes I can pay more for one of the Econo-plus seats ... but I should not have to. 6'4" is not average, yes, I realize, but so what---it's a genetic tax then? If I want to fly I have to pay more? If I were too "wide" you might say (though you shouldn't), my fault, I should lose weight. But what am I supposed to do? Saw my ankles off?
If I were the worlds tallest person, sure, you could claim exceptional circumstances. But 6'4" is not that exceptional, I submit to you.
PS I'm not criticizing you of course... only making the point that for many of us, this has become an exceptionally frustrating (and costly) experience.