A Recommendation: Use GoodRX for low cost prescriptions

What’s going on with prescriptions? I have saved more than $100 for each of two prescriptions in the past couple weeks using GoodRX. I usually have obtained my prescriptions at a nearby CVS; however, recently I discovered that prices at CVS with insurance coverage are more than 10X the price I get using GoodRX at pharmacies located at nearby grocery stores which are not using my insurance coverage at all! How can this be?