You're all missing the point here.
Sure it's a rip-off.
Which is why it is also an opportunity for some enterprising soul. Namely setting up a "Convert your AA 2500mAh battery to a D 2500mAh battery with this handy shell for a simply amazing price of $1.99 a pair". Any Chinese manufacturing shop should be able to turn out 1000's of those blanks for $0.05c a pop. The rest is all moolah for you.
Any takers - and I want 5%.
Then you'd see how fast the price would come down!