One thing that you have to accommodate in this assessment, is that Yamaha run the worlds largest networks of music schools, and new musicians coming into, and subsequently graduating from those schools often had a fixed budget for their instruments.
The DX9 was Yamaha's way of marketing to those schools in a fashion that would imply affordability, while giving access to the 'professional' tools that commercial musicians would use (DX7). The idea being, the student starts off on the DX9/DX100/DX21 and then - when they graduate and can eventually afford it - upgrades at a later date to the DX7.
They used this strategy very successfully for decades, to expand their market and capture devoted fans of their instruments. Even today, Yamaha's product lines are designed to be affordable to students, and eventually when those students become professionals, provide a 'guided upgrade path' to the higher end products.
The DX9 was Yamaha's way of marketing to those schools in a fashion that would imply affordability, while giving access to the 'professional' tools that commercial musicians would use (DX7). The idea being, the student starts off on the DX9/DX100/DX21 and then - when they graduate and can eventually afford it - upgrades at a later date to the DX7.
They used this strategy very successfully for decades, to expand their market and capture devoted fans of their instruments. Even today, Yamaha's product lines are designed to be affordable to students, and eventually when those students become professionals, provide a 'guided upgrade path' to the higher end products.