If cost is important to you, consider this - there are plenty of non-"AT" skis that will work just fine in the backcountry. I'm thinking of some of the more shapely skis (not full-blown shape skis) and earlier models with lots of sidecut that may be sitting in the 50% off sale rack right now. I saw some discounted skis last fall for $75 - $100 that would've worked beautifully as AT skis. If you know that flex characteristics you're looking for (soft shovel and tail) and how to size up a ski, there are a lot more options than a $400 pair of specialized boards.
Nothing in the world is more yielding and gentle than water. Yet it has no equal for conquering the resistant and tough. The flexible can overcome the unbending; the soft can overcome the hard. - Lao Tse