Factual error: At the beginning of the movie, the main characters are supposedly in Amsterdam, but everyone is speaking German, it's not just the main characters doing this.
Factual error: In the beginning, the Amsterdam redlight district is shown. They have shown windows on which sex scene shadows appear. Actually, all redlight windows in Amsterdam have big red-colored thick curtains which are closed when any customer gets in with the prostitute. There is no way that shadows can appear and visitors can see it from outside. Doors are also closed from inside, so it is not possible to open it as shown in the film.
Factual error: When Paxton arrives at the station at the end of the movie he is supposed to be in Germany, yet there is a sign on the platform which reads 'Praha'. Also watch out for posters and signs in bad german language like an add which reads 'Neu am DVD' (should be 'Neu auf DVD') and a sign with 'Dieser Bahnhof wird Video - bewacht' ('Dieser Bahnhof wird videoüberwacht') on it.
Factual error: When the girl has her eye cut off, pus begins to pour out, but realistically there is no reason for this to happen. Pus is only present where infection has set in, and the wound literally just happened moments before, medically it's not possible for any infection to have begun.
Factual error: The amount of blood that comes out of the main characters hand when his fingers are cut off is too much to be realistic at all.
Factual error: At the red light district, the windows are not lit up red. They're rather lit up blue, meaning these would be all transgender/transvestites.
Answer: This is actually a reference to both Eli Roth and Quentin Tarantino's experience with the same hooker. After both Tarantino and Roth "had" the same call girl without either of them knowing, the hooker replied to both of them as she left their separate rooms, "I get a lot of money for you, and that makes you MY bitch. Hence, the opening line for the trailer. Both of them had a big laugh during the premiere.