Sounds, capability, and better construction. It really depends on what you re looking for. The Casio Privia PX130 is great if all you need is a stage piano with a few sounds. It give you limited capability to do sequencing etc.... It has a great feeling weighted/hammer action.What do the $2000 keyboards give you that the $200 ones don't?
I got started by borrowing a Korg DW8000 analog synth from our old bass player. The acoustic piano sound really stunk, but he had programmed a nice crunchy clav sound in it, and the organ sound was tolerable. For a while, I used an old "Proformance" sound module just for its acoustic piano sound, connecting it via MIDI to the DW8000, to get around the bad piano sound in the DW8000.I'd just try to use my guitar amp, works at home with my '80's Korg synth!
No way to compare a low-end Yamaha to a Motif. Not enough space here to say how much better one is over the other.What do the $2000 keyboards give you that the $200 ones don't?