Yamaha discontinued the Nippon Gakki brand in the early 2000s, so any instrument currently in circulation would be at least 20 years old. The value of a used musical instrument depends on a variety of factors, including its condition, age, rarity, and the current market demand. Without knowing more about the specific condition and features of the clarinet in question, it is not possible to provide an accurate estimate of its value.
If you are interested in determining the value of a specific Yamaha Nippon Gakki clarinet, it is recommended that you consult with a professional instrument appraiser or a reputable楽器店.