In general; a $2 cup of coffee in north america costs 2€ in Europe. A $300 Wii U in north america costs 300€ in Europe. The only time currency conversion matters is because you are converting between two currencies, when buying a product from another country.
GOG.com sells all their games in north american prices because it only has offices in north america. You are buying a product from north america when you buy from them. Dropbox, Steam, Nintendo, Sony all have offices in Europe. So you aren't buying a foreign product and you do not account for a currency conversion as there isn't one.
Taxes are an important consideration. For example if you buy a $500 cell phone from north america and have it shipped to Europe. You will pay less for the phone but when it crosses the border you pay considerable taxes such that the "deal" is no longer worth it.
If import taxes were applied to physical as well as digital goods, as they probably should be, you would actively want to buy from a European company within Europe. You currently do for most goods, because it actually saves you money.
It's the lag on charging tax for imported digital goods. Otherwise you are earning Euros you are spending Euros, there is no currency conversion.