I understand your point of view. But first of all, Stones is not a random DM he will be very good and much better than Lescott. Also, Everton will sell him.
I don't think that we can comparate English premier League and Serie A.
When you see that:
The 11th in BPL win 100 M€ when Juve win 111M€.
To refuse an offer of 120M is very difficult especially when the player want to leave. If you refuse to sell him you have 60% of chances that he will play a shitty season.