Insurance vs no insurance

I had something interesting happen at Meijer pharmacy yesterday. Dr Davison, my doctor ordered some new meds for me. (an antibiotic called tetracycline). When I showed up, my co-pay was $9.63. Normally my co-pays are $10,$20 or $40. I asked him if they had run this med through my insurance. He said no, so he ran it through.

It came back after insurance that my co-pay was now $10. I was like without it, I only owed $9.63! This was by far the first time that that's happened. I got to get it for the lesser amount. For what it's worth, it doesn't hurt to ask (on the flip side, I have a med that I get for free, since it's a specialty drug, that costs $4400 for a 28 day dose. That one I'm happy about!)