How do I spend less on protein without buying junk?

Four levers, in order. Buy on dollars per 20g of protein, not sticker price — big bags of whey concentrate usually win. Use subscribe-and-save where the discount is real and the cancel terms are easy, and factor the subscribed price into the comparison. Prefer larger sizes once a product has proven itself, treating the first small purchase as a paid trial. And do not confuse cheap with unverified — a bargain tub with no published testing is a different risk than a bargain with a certificate. Our cost-savings tables rank products on exactly this math.