MAC You Wouldn't Get It is a neutral pink with a semi-matte finish that is permanent and retails for $19.00. In comparison, YSL Arlene's Nude (121) is a neutral mauve with a satin finish that is limited edition and retails for $38.00.
YSL Arlene's Nude (121) is 80% similar — it is lighter, warmer, glossier.