MAC Rich Core is a warm plum with a pearl finish that is permanent and retails for $20.00. In comparison, Natasha Denona Smoky Plum (23P) is a warm plum with a pearl finish that is permanent in palette and retails for $29.00.
Natasha Denona Smoky Plum (23P) is 85% similar — it is less shimmery, cooler.