If that were the case of taxes/tariffs then the real price should be depending on your actual country and not the continent as a whole. Even in the US there would be no single price either, since there are some states where there is no VAT compared to others where it's quite high. So, yeah, i'm pretty sure it's a way to make easy money for the publishers. Sad to see Valve supporting this, really.

They don't have VAT in the US, and their sales tax is a bit different. I'm not sure if it applies to digital purchases.

However, the price difference is often larger than what taxes alone would suggest, but surely localization plays a part here. Still, many European countries would need a reduced price just like the developing countries (to a lesser extent) to have an equal purchasing power compared to the US.