I'd say Yamaha discontinued the 9000 Pro because it had numerous hardware issues that could not be addressed by a software update. Poor sales were a direct reflection of the problems caused by the slow CPU Yamaha decided to use in the 9000 Pro. Word travels fast when problems arise and Yamaha knowing the 9000 Pro was plagued pulled the plug. They made sure the CPU in the Tyros was faster after all the problems they had with the 9000 Pro. You can be certain had Yamaha used the same slow processor in the Tyros, the Tyros would have failed due to numerous hardware and software issues.

It's easier to dupe someone when the intended purpose is for home use and most users aren't savvy. I think Yamaha figured business as usual would work in the Pro Market but it backfired. Serious pros need an instrument that will do what the manufacturer claims and works 24 hours a day 365 days a year. Since the 9000 Pro's demise I believe Yamaha has decided to stick to selling home keyboards which is why the Tyros and PSR series sells well.