Based on your comments, I can only assume that your clientele also involves other dealers and collectors beside musicians. Your regular professional musician that might be interested in purchasing a high value instrument, will immediately take it and test it against other valuable instruments and in different acoustics/settings. That’s where the magic happens and the truth reveals itself—on the stage.
Now, based on your vast experience as a dealer, could you please answer this question: What is the percentage of professional musicians that might base their purchase on the condition of the instrument, and how many on the acoustic qualities of said instrument? Before giving an answer that combines the two, let me follow up with another question: Which of the two elements is in your opinion more important in the eyes/ears of the musician?