Building a traveling bike, frames and components: where to buy in Europe
European prices always include VAT, and US prices are typically announced without sales tax (or customs, if you really intend to order from US). Once you add the sales tax, the prices are closer.

Generally, you will pay extra for a brand that is commonly not available in Europe. In addition to Surly, Thorn is easily available in Europe from UK and cheaper than Salsa.