Circumstances, innit.
George Saville was Millwall's best player last season, is 25 and had two full years left on his deal. They were absolutely desperate not to lose him, especially as they had limited/no time to replace him.
Gary Madine was 27 when Cardiff bought him, strikers always come at a premium, he'd scored 10 goals in half a season for a terrible team in the Championship (again, he was their biggest asset). And Colin has form for ridiculous striker signings in the middle of the season.
Romain Saiss is nearly 29 (or will be by the time anyone can buy him), 18 months left on his deal, hardly plays and I doubt we're going to make that much of a fuss to keep him if he wants to go. Every chance he won't have started a league game all season when the window opens.
He's a miles better player than the first two but the situation dictates that he won't cost as much. Plus you can't judge player values on someone else being an idiot and wildly overpaying for an obvious pup.