I get so tired of hearing this. The NFL is not paying PFF for their player grades. There is a ton of stuff that PFF provides the NFL teams that isn't even available to the public. I have posted a few times now everything the NFL gets for that money. Player grades are a microscopic data point compared to what they receive for that money. Just because player grades are part of the package, doesn't mean the NFL takes any stock into those grades.
For example, PFF provides NFL teams with things like how often a team runs each formation, what type of plays are run out of that formation and how often. What teams run on each down, etc. Things like that are what is valuable to an NFL team each week when a team only has a week or less to prepare for an opponent. I doubt any team cares that PFF rates X player 84.5 or 24.3. Thats small potatoes.
This is what teams pay for: https://media.pff.com/2018/08/PFF-Play-Data-Fields.pdf