The promotion-chasing Championship club have protected themselves against their captain leaving on the cheap this summer. And that sends a strong message to suitors such as Tottenham, who were baulking last term at paying £25m for the former England Under-21 midfielder.
Grealish agreed a fresh five-year deal last September as Villa's new owners Nassef Sawiris and Wes Edens flexed their financial muscles.
The fact that the 23-year-old has a trigger in his contract has been known for some time. However, estimates of the figure involved have varied between £30m and £45m – an the figure is way in excess of that.