I have run into a similar problem on European river cruises. We are looking into doing a river cruise in the next couple of years, and have gotten several brochures from different companys. My Aunt and a cousin were visiting from Germany this past summer and I showed my cousin the brochures and the itinerary we were planning on. She was flabbergasted at the prices we are charged in the US. She had cruised on of the lines the year before at half the price. She has checked with her TA in Germany about us booking through her and it cant be done. So in the next couple of years we will be going to Germany for a visit and taking a river cruise with family that will cost us almost double what their fare will be.