Oooops,

Previous comment would be regarding the lower price for SD-1 in Europe then in US.
I have just noticed that you were comparing its price with X1.
Sorry ...that is a different story.
I think the reason for lower price then X1, as someone mentioned before could be the speakers which could demand more expensive production process or X1 is just more popular than Sd-1 in Europe.
I know that many people consider 5 octave enough for an arranger. I agree with that.
Of course if you want to play some jazz or classical compositions with you special voicing you will need more space for both hands but just few of them use an arranger for that.
When I want to play jazz or classics I need to move to 88 piano keys because nothing can replace that feeling, not even SD-1's 76 keys.
That's why 76 keys on SD-1 could be seen as "too big to fit in my car" and not so pupular like X1.
Maybe I am wrong ...

Cheers