Prescription pricing shenanigans

One of my prescriptions, usually $10 for a 30 day supply (generic) was $30 today with my new insurance. In looking at the prescription closely I realized the pharmacy gave me the name brand, not the generic. When I went back and questioned, they told me that my insurance company rejected the generic prescription and forced me into the higher cost brand name. WTF?

So I checked their website, and this is what I see.

Generic - my cost $50, plan pays $39. Name brand - my cost $30 - plan pays $107.

Huh? The only way this makes sense is if they are getting some sort of huge kickback from the brand name manufacturer. Why else would the insurance company voluntary pay 3X as much as it needs to? This is a fairly common drug that has been around a while, not some exotic cancer treatment anything weird like that.