Sounds about right.
Sky say £25m with £5m in add ons fwiw.
Doesn't say how the £25m is structured though, so it could be £15m upfront and then £5m each season. Unless Everton sell him in January, then they get him for free.
I got those figures from Everton press and fans, but yeah there is not a chance of Sunderland seeing that much upfront.