It isn't so important now with all these fancy General Arranger keboards however........
In the good old days we had ONLY work stations and Midi.
Songs were manufactured by using midi one layer and track at a time. We often used several keyboards for a given song to get the sounds from them.
When we played the song in the studio or mastered it all the keyboards used played at once time with the sounds and tracks that were used from each individual keyboard. Have times changed?
Now we push a button and record a song and play it all in one keyboard.
But as Rikkie sez: Now it is too late to get a decent price for keyboard so we save them to sell as antiques to the next generations. As Junk we can get huge prices for them
Best to all