The Ordinary dupes list

Niacinamide 10% + Zinc 1% ($6) for Paula's Choice 10% Niacinamide Booster ($53). Retinol 1% in Squalane ($9.90) for Sunday Riley Luna Retinol Sleeping Night Oil ($55). Lactic Acid 10% + HA ($9.20) for Sunday Riley Good Genes Lactic Acid Treatment ($85). Multi-Peptide + HA Serum ($19.90) for SkinCeuticals P-TIOX Anti-Wrinkle Peptide Serum ($150). Glycolic Acid 7% Exfoliating Toner ($13.50) for Paula's Choice Skin Perfecting 8% AHA Gel Exfoliant ($37). 100% Cold-Pressed Virgin Marula Oil ($11.40) for Drunk Elephant Virgin Marula Luxury Facial Oil ($72). AHA 30% + BHA 2% Peeling Solution ($9.50) for Drunk Elephant T.L.C. Sukari Babyfacial ($80). 100% Organic Cold-Pressed Moroccan Argan Oil ($7.80) for Josie Maran 100% Pure Argan Oil ($39). 100% Organic Cold-Pressed Rose Hip Seed Oil ($10.90) for Pai Skincare Rosehip BioRegenerate Universal Facial Oil ($54). Ascorbyl Tetraisopalmitate Solution 20% in Vitamin F ($20.50) for Sunday Riley C.E.O. 15% Vitamin C Brightening Serum ($50). Hyaluronic Acid 2% + B5 ($9.90) for Glow Recipe Plum Plump Hyaluronic Acid Serum ($38). Retinal 0.2% Emulsion ($14.90) for Medik8 Crystal Retinal 10 ($111). Multi-Peptide + HA Serum ($19.90) for Medik8 Liquid Peptides Multi-Peptide Serum ($68). Azelaic Acid Suspension 10% ($12.20) for Paula's Choice 10% Azelaic Acid Booster ($42). 100% Plant-Derived Squalane ($10.40) for Indie Lee Squalane Facial Oil ($32). Ascorbyl Tetraisopalmitate Solution 20% in Vitamin F ($20.50) for Medik8 C-Tetra Lipid Vitamin C Serum ($53).

Niacinamide 10% + Zinc 1% ($6) for the Paula's Choice 10% Niacinamide Booster ($53), about 92% less per ounce. Same active at the same strength: 10% niacinamide, second on both lists right after water, in a thin serum for pores, oil and uneven tone.