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Is this a mistake? It's the same price on steam.
The Steam price does not really matter in that regard. Its there to offer compensation for exchange rate differences. And the Devs/publisher already adjusted some of the prices. For example the US dollar price of the game is 19.99$ while the Euro price is 16.79€. With the current exchange rate this is one of the few rare cases (actually the first one I have seen at all) where the people paying in US dollar might receive the store credit. (19.99$ = 17.50€)
Ah, thank you!