Read somewhere, Adidas keep all profits from shirt sales. So really, Utd make nothing back in shirt sales from Pogba
It's been said before, but even if we got all the profits from Pogba shirt sales, that would be a tiny drop in the bucket of what he brings commercially to United. He comes to United, he becomes the new face of the club. Rooney's career is winding down, Zlatan is only here for another year. Rashford and Martial seem pretty quiet. United need someone that sponsors will be excited about having their face all over their product. He will attract new sponsors, as well as increase the renewal fees for current sponsors.
He is also one that is starting to get in with celebrities and superstar US athletes, and I see this to continue and grow, especially with the publicity that he'll get over being the most expensive footballer ever. Adidas will likely also get him to events in future off-seasons with other stars of theirs, have them all start hanging out, following each other on social media, etc. All of that raises the profile of Pogba and United. He can also become the first football/soccer player to really appeal to the urban youth in the US. He's already considered one of the most marketable athletes in the world, and when you add in United's marketing pull, the commercial possibilities are endless.
Make no mistake, as much as we want a great midfielder like Scholes on the field, we wouldn't be splashing 100m on him if he was like Scholes off the field (i.e., quiet, reserved, almost a homebody, etc.--all things that we loved about Scholes, but not things that marketing people in modern football would have loved).