Allantoin

Product	Size	Strength	Best price	Per ml of active
10% Niacinamide Booster Paula's Choice	20 ml	unstated	$42.40	—
— 10% Azelaic Acid Serum The Inkey List	30 ml	unstated	awaiting retailer	—
— Buffet The Ordinary	30 ml	unstated	awaiting retailer	—
10% Azelaic Acid Booster Paula's Choice	30 ml	unstated	$33.60	—
Multi-Peptide + Copper Peptides 1% Serum The Ordinary	30 ml	unstated	awaiting retailer	—
— 0.3% Retinol + 2% Bakuchiol Treatment Paula's Choice	30 ml	unstated	awaiting retailer	—
— 1% Retinol Treatment Paula's Choice	30 ml	unstated	awaiting retailer	—

Cost per active is price divided by the volume of pure active in the bottle. It appears once retailer prices are being tracked, and only for products whose strength the maker publishes.