What does Avery say that offends berience in the piano lesson?

In "The Piano Lesson" by August Wilson, Avery offends Berneice by suggesting that she should sell the family piano to solve their financial problems. This suggestion is deeply disrespectful to Berneice, as the piano symbolizes their family's heritage and history. The emotional weight attached to the piano makes her feel that he doesn't understand the significance it holds for her and her family's legacy.