From a sporting perspective, the last 6 years have been a failure for both parties, so it’s best that he moves on and we start building our squad with young, hungry players fitting how we want to play.
From a financial/commercial perspective, keeping him even at the cost of doubling his wage is the rational move, as hard as it is to stomach the thought. The increase would amount to ~ 50m transfer fee over a 5 years contract. It’s almost a guarantee that we won’t be able to get anyone in for 50m and replace Pogba’s commercial value, in addition to the bonus that if we decide to sell him in a year or two we can recoup some money instead of none. Of course, there is possible fallout from other players wanting the same deal when it comes to their renewal, but that’s already a reality when you see how many of them are choosing to run their contract down nowadays.