Like, 5 dollars maximum I expected.
No big deal though, probably get it on sale some time.
I say 5 to 10 because I think of the work put into the cosmetic packs for something like EU4 as:
-Take a base 'human' model and bedazzle it
-Now put that bedazzled human model on a horse
-Now put it on a cannon
-Repeat two to four times
Where as for Stellaris the the production looks more like
-Create fifteen new 2D images capable of small amounts of movement without tearing
-Now make a new corvette model
-Now make a new destroyer model
-Now make a new cruiser model
-Now make a new battleship model
-Now make a new transport model
-Now make a new construction ship model
-Now make a new science ship model
-Now make a new colony ship model
-Now make a new space station model
-Now make a new mining station model
-Now make a new terraforming station model
-Now make a new observation post model
-Now make a new wormhole station model
-Now make a new defense platform model
-Now make a new defense station model
-Now make a new fortress model
-Now make a new city background image
-Now make a new frontier outpost model
And presumable this is all from scratch or taking small shortcuts where they can.
So no, 5 to 10 bucks sounds about right.