That is only true of the PSR line up. They are made cheap to be priced cheap. the 9kPRO is a professional keyboard in every sense.
It feels great, it's solid, and has all the bells and whistles to keep you busy for a long time. The only drawback (for alot of us) is the LACK of speakers, the extra length and exsessive weight. If you have a roady, or don't move it much .... it's the BEST all-in-one keyboard I ever saw.
Oh yeah .... it's expandable too.(sounds AND polyphony)