There's at least a few of us (Euro nations) who pay in native. Common Sense is listed on Steam for me at 99.99 NOK, which is 10.89 EUR atm. *shakes fist at conversion rates*It states the price in euros and I pay in euros, without conversion. They just don't take non EU countries into account when they form the prices. You have 2 tiers of European countries on steam, EU members and states out of EU. All pay in Euros, but those out of the EU don't have the VAT so it shouldn't be in the price. I will buy the expansion anyway though.
Anyway, I'm almost certainly picking it up even at the (about) 20 EUR price, it'll still provide me with 60-100 hours of game time all on its own I'm sure, making it far cheaper than most other entertainments.