Amazon has the 4.5oz Neutrogena T/Sal Therapeutic Shampoo for $7.79 - 30% off coupon (check "Save an extra" box, eligible on first S&S order for this product) - 5% off with Subscribe & Save (can cancel at any time) = $5.06 with free shipping on $35+ or with Prime.

Contains 3% salicylic acid, a clinically proven active ingredient and treats symptoms caused by scalp psoriasis, seborrheic dermatitis & dandruff.