It is not just an adapter but there is lots of electronics in there and they sell only very few of them so that's the reason why they are so expensive. German dealers sell the TopolinoIII (PS/2 mouse adapter) and the Lyra (PS/2 keyboard adapter) for about 30 Euros (32 US$) each.
Perhaps you should consider buying a Highway USB controller for about 100 Euros (110 US$) and use standard USB keyboards and mouses and other hardware (e.g. flashcard readers, ZIP drives, digital cameras etc.) from now on.
Bye,
Thomas
