Sydney Grace My Constellation is a warm plum with a metallic finish that is permanent in palette and retails for $6.25. 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 90% similar — it is less shimmery, darker, cooler.