I don't know if Yamaha is dominating the arranger market...I seriously doubt it..
I think as an example[from what I read], Roland is more favorable in Europe..
Yamaha is brought to our attention because all the Yamaha owners are here at SZ

..
Yamaha has a broad base of sales because of the PSR line [also includes all the other "toy" models]..I would be curious to know how the PSR stacks up against the same price point Casio line...my money[bet] is on Casio...world wide..
I wouldn't feel bad for any of the major companies..there is enough of our dollars to go around..
Maybe we should start supporting the small independents........like Domenik...I am sure there is a future Mediastation on my horizon... :}