Viperfdl has the right of it. Like how a brick and mortar store follows the MRSP (manufacturer's reccomended sale price), the digital distributors are provided a "recommended" price by the publisher of the game. Traditionally, a brick & mortar could undersell the MRSP, but they would be cutting into their own margin. Walmart and other big box stores are a prime example of this -- they take a reduced margin in order to outsell their competition, making it back on volume, in theory.
Also traditionally, some manufacturers looked poorly on big box stores underselling the MRSP, and sought to enforce it through product retaliation (no shipping of product unless guarenteed to sell at MSRP) or other means (lawsuit anyone?). I am not familiar with how this relationship has transferred from brick & mortar to the internet, and would actually be quite interested to hear from Frogboy on how it all works, but I might be wierd that way.
What I'm getting at, is that in all liklihood the MRSP is being set and enforced on Stardock by the publisher of the game. Maybe there's room for Stardock to negotiate on the price (say for sales and such) with the publisher, maybe the publisher is holding firm, I have no idea. What is happening though, is that you're paying more value for the game than people in other parts of the world. This is nothing new. I remember at least, that in Austrailia, Yhatzee (of Zero Punctuation) has complained numerously that his bosses are overcharged for these games. However, the wonders of the Internet make it abundantly clear to you just how much you're being soaked.
Another theory, is that Stardock's Dollar to Euro converter is broken. I can't really speak for that though. I can say however, that when I was last in Thailand, Stardock's currency converter worked just fine to turn my Thai Baht into Dollars to buy a game.
TL,DR: viperfdl is right, it's probably not stardock's fault, and yes, you're getting soaked.