I wouldn't have a clue.
He has intensity and can move the ball quickly but he has flawed technique and has bad lapses of concentration but yet he is a regular for Brazil.
25mil??
Like a lot of things, not everything because the market operates in a state of irrational exuberance for the most part, it comes back to supply and demand doesn't it?
For the things Fred can provide is there another midfielder who can do the same things (supply) and how much does X club want Fred, specifically, to do those things rather than another option (demand).
Looking at it like that, I find it hard to believe that you could convince many clubs to part with more than £15-20m for Fred.
Fred is, undoubtedly, a pressing machine. He's a great character. He never gives up. All of those are desirable traits. BUT they're not unique. Fred is better than a lot of players at this stuff but he's not the only player in the world who can do it. You can go and snatch someone up from the Red Bull group who will happily press all day for you. So then you're asking how much does it
have to be Fred? I think most clubs and coaches, Tite excepting, will answer that question: 'It doesn't really need to be Fred.'
So if you're putting the player on the market you have to make it attractive for other clubs, who might have other cheaper options who can do similar things, to buy him. Then you factor in the huge wages Fred will be on, as a United player. That will act as a disincentive for the clubs who might be interested in him. As most clubs who could match those wages won't be interested in paying them to a player of Fred's quality.
As others have said his contract length is pretty short too.
All of this, to me, puts a downward pressure on the price.