I don't quite understand the over emphasis on his goal ratio at 22 years old.
It is highly unlikely he will be the next Jamie Vardy, but Vardy was playing in southern area division 1 at 22. Wasn't Harry Kane doing nothing at Leyton Orient, Norwich and Leicester at a similar age?
Point is, Boro along with with the other clubs who wanted him Rangers, Celtic, Hull, Leeds, Sheff Utd clearly believe he has potential.
If he was 22 years old and scoring 25 goals a season in the championship he is worth £15m and signing for someone like Everton.