For Prime members only, Amazon offers the Quest Protein Bar in Peanut Butter Supreme for $2 with free shipping. (Other eligible flavors are available here.) Plus, you'll get a $2 credit to spend on select nutrition bars. Assuming you'll use the credit, that's tied with our November mention and essentially like getting the protein bar for free. (It's a low by $2 after credit.) Each includes about 20g of protein.