Buffet owns stocks in productive companies. If he starts selling this stock and gets enough money for his statue, by definition he's absorbing market capital that would otherwise be invested in productive companies. So he's effectively shifting investment from jobs in companies to jobs in giant statue production. The effect on the middle class jobs is largely nil.

If a billionaire is entombed in a safe with his symbols of wealth forever, it's as if his symbolic wealth ceases to exist. Effectively, the symbols of everybody else become more valuable to reflect the total quantity of products and services available. It's just like burning money, no wealth is destroyed, just redistributed to everybody else who holds the same currency.