It's not as bad as Steam's recent 1$=1€ fiasco, which made their games about 25-30% more expensive if you live in europe, and much more expensive than buying a physical copy locally 
It's not just a Stardock thing either, this is pretty much the norm for games that are distributed both digitally and physically. The retailers don't buy the games at the full price, since there after all has to be a profit in it for the retailers. Buying wholesales also tends to get them a discount, since they are after all taking a risk buying a lot of game copies they might not sell. If the digital version massively undercut the retail versions, then a lot of retailers would simply not stock the game at all, which would mean a fairly significant loss of total sales in the end.
Personally, it's not a big price difference for me, in fact most of the time I would end up better off with the digital copy due to international shipping prices, customs handling cost and the 25% sales tax that would be incurred (which is incurred not only on the game price, but the shipping cost as well). Anything physically imported that costs more than 200 NOK (~$28) has to be declared and have tax added to it. The sad thing is, this value limit was set in 1975(!) and has not been adjusted for inflation or anything else ever since. The last game I ordered physically was the Lord of the Rings Online: Mines of Moria expansion, which cost me $23 extra in customs handling and tax after it entered the country, and whatever I paid for shipping came on top of that.
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