20 grams cost $25.00 at my dermatologist's office. The nurse practitioner and the doctor I saw said they recommend this to all of their patients, and they use it themselves. (A small percentage of the population cannot tolerate retinoids). This is Rx only, but they had it on hand, so I didn't need to go fill a prescription. I should point out that they started me out with a lower dosage (it was the lowest one, and I think that was 0.25%), and I tolerated that well, so when the tube ran out, they upped my dosage when I went back for more. When my dermatologist first started me on Tretinoin, he advised me to use a pea sized amount (1 gram) mixed in with my moisturizer every other night. He told me that if my skin seemed to be tolerating it, that after a month, I should start using it every night. All of that worked out fine. When the nurse practitioner prescribed the higher dosage, she said that (0.05%) is what she uses, and even she couldn't tolerate it every night. So, this is what I have been using, and I go by how my skin looks. Sometimes I use it every other night, sometimes every third. When I use it too often, my skin tends to get irritated, red and, sometimes, dry & flaky. I love the results I've seen with this product - reduction in fine lines, my freckles are hardly noticeable, and it helps with acne, too!