Are the vehicles you are looking for not made by any other manufacturer? I have a ten-car train of Maerklin 'ozeanblaus' for my Aster Br01. Five were bought from the loco Marklin dealer who used to operate from his house hard up against the back fence at a nearby USAF base and cost around £350 each, and the other five came from a G1 show and cost £60 each. I defy you to tell the difference....
KM1 models are nothing less than gorgeous, but even the basic old-style passenger coach is hitting up against the £700 mark, and are currently all sold out according to the website.