if we are being told Tammy is around $40m, then why should Willock go for any less. Willock had the best goal scoring record of any player at the back end of last season - and can anyone be confident that Tammy has a higher ceiling?.
Willock had a goal scoring run in a team that played to his strengths (as we find out). That's likely all it was.
He had a 'good tournament'. Only stupid cash rich clubs spend serious cash on players without any history of consistency. Granted, if he carries on then it becomes consistent.
Keep and loan. Gamble that his value increases.