I was shocked to find that some of my prescriptions that were costing me $20 out of pocket with insurance at Rite Aid where $4 cash price at Walmart. I've moved everything I can to cash at Walmart, even in some cases where the Walmart cash price is a little higher than my with-insurance price elsewhere, just on the general principle that I don't want my insurance company to know what drugs I take [1].
[1] This stems from a time once when a condition I had improved to the point that I could stop taking drugs for it. A few months later it returned, and I asked my doctor to renew my prescription. He did so...and the insurance company rejected it. They were treating it like I was a brand new patient, and they no longer allowed that drug unless you had first tried a couple other newer drugs and they were not acceptable. I'd never had those drugs, but I'd had others in their families and they were either not very effective or had annoying side effects. I was willing to try the new drugs eventually, if this relapse turned out to not be temporary, but in the short term I wanted what we already knew worked well.