We couldn't get £40m for him as no one else wanted him at all, even for the £23m. So that's his value.
The fee makes a bit of sense when;
We were looking to sell him (one of the main reasons really), doesn't fit in the way we play, injury prone, had no effect on our best season in a very long time so wasn't really a key player any more, his poor goal and assist return (1 assist in 2023!), incredibly inconsistent.
He is enjoyable and fantastic to watch when he's on it, but he is on it rarely and that really doesn't sell well without g&a numbers.