The veteran Uruguayan striker has agreed a one year contract extension at the club, despite hinting earlier in the season he wanted a return to South America.
"If you look at the policy over the last couple of years since Solskjaer has come in, I don't think they will sign a striker now Cavani has signed," Neville said on Sky Sports.
"They have been desperate for Sancho but didn't get him last summer and were criticised for that, but they could look incredibly smart if they could get him this summer at half the price, having waited 12 months."
On the news of Cavani's re-signing, Neville added: "It's massive news for Manchester United.
"I was one of the sceptics when United signed Cavani, thinking about how windows had gone in previous years where players were signed late on with an air of desperation when United hadn't signed their main targets.
"But he's been absolutely sensational in every single way. Forget the goals; his attitude, commitment, and his impact on the other players has been sensational.
"Manchester United can press better when he is on the pitch, they have a better target man to hit.
"He's a throwback, a classic centre-forward who makes brilliant runs that you would have been taught 20 years ago.
"He's been an absolute joy. We questioned whether he could do it for Manchester United, but he has done it and I'm delighted that he's going to be there next season. They are a better team with him in and he is in their best team.
"He's always in great positions. The timing of his runs and his finishing from those positions is the best in the league. His heading is absolutely wonderful, as is his work ethic.
"Without him, this season would have been completely different."