Fees for checked luggage, I can understand... the more bags you bring, the more weight you add to the plane. Fees for checked pets, I can understand, too, for the same reason (as well as to offset the liability that the airline incurs when transporting the animal in the hold), though I agree these are still fairly high.

But fees for in-cabin pets? Sure, it's a bit of extra weight (max of 20 lbs for pet, carrier, and supplies), and therefore some fee is justified. (I wouldn't begin to recommend raising fares to allow free pets, because 99.9% of passengers don't fly with pets - why should they pay for my pet to fly?) My beef is not with the fee, but the ridiculous amount of the fee, given that the airline incurs only minimal liability and essentially no added labor for in-cabin pets.

(Here's the real butt-kicker, though: since your pet counts as your carry-on, if you're not an elite member you have to pay the in-cabin pet fee and the checked bag fee. At the very least, you'd think they'd exempt you from the checked bag fee... and maybe they do, I haven't actually tried, but I doubt it.)