(The title currently just says '2,99 per month'. This should probably be changed "2.99€" instead, since a lot of people would expect HN to default to USD. Even I (living in Germany) was surprised it was in Euro.)
Agreed, though the tip-off to me that it wasn't USD was the comma. For anyone else like me 2.99€ is $3.36 USD.
I didn't check if they do, but they should not charge VAT for customers located in the USA. Which means that the price will actually end up being $2.80 (as of right now 2.99/1.2 EUR to USD).