I wonder if anyone else is also interested in Harry Wilson. 15m seems higher than I'd expect, unless there has been some other club involved.
It's a bit of a conundrum with Harry. For us, he's nowhere near the team, and everyone (even Fordy, I suspect) knows that. Best quality backup to Mo is Mane, with Jota coming on to the left. Other backups at the club for the right-sided attacker that are better than Wilson, either in 433 or 4231, are Shaqiri, Oxlade-Chamberlain, Minamino and Jota, and possibly Origi and Elliott.
So buying clubs would be expected to drive the price down, knowing this. And yet we need to be careful not to undervalue him. Harry's got a wand of a left foot, and in the right set-up will win games for his team with that weapon alone.
Joining those two lines of thought together, I'd have expected him to go for about 10m, with maybe a few more millions in add-ons. However if there is also another club interested, that might have pushed the price up.