I just searched SD for Similac Pro Advance and saw a Rite Aid banner ad for 30% off. It says Members Only but Rite Aid membership is free, so...
It comes out to about 91 cents/oz. Not as good as Amazon's periodic 35% coupon at 60 cents/oz (which seems to have just expired) but better than Target's 4-pack restock $1.02/oz which requires a REDcard and way better than Target's current $5 gift card offering on 2.
It's a super long URL, hope it works for others! Also get 3% CB from Rite Aid at some popular site.
EDIT: do NOT click the save 20% or apply the SAVE20 discount code. It applies to regular retail prices only and will remove this deal from your cart. You'll need to empty your cart and go to the URL below again to get the savings.