I don't think Yamaha arrangers are over priced? They are usually comparable to anything else out there in the similar range especially at launch. The SX900 is still relatively new and will still fetch full price whereas the Pa1000 for example is a couple of years old now so I would expect it discounted as mine was when I purchased it.
Ok let say then every mid range and topl arrangers are overpriced. Look what you get with a Yahama modx synth. Why is this instrument only 1100 euro? Sound much better to me then any arranger out there and is full with features and also very important has usb audio.