Now it's 19,99 as supposed.
It's not that difficult to understand why they f*cked up - someone thought it was in line with the "other DLCs" (spritepacks) which are listed 1,99 as their normal price.
I'm 100% certain that Pdx will precheck prices beforehand from now on. At least if the merchant doesn't fully cover for their mistakes.
10 minutes with 1,99 - well, at least it isn't as bad for Pdx as 3,99 would be with CK2

Even if the losses for games sold with that amount wouldn't be that much, it would mess everyone's price expectations for a new game. Expansion like AHD is smaller fish compared to that.