Louis van Gaal's side splashed out 38 million euros to sign the 18-year-old left back from Southampton but the former France defender believes he will prove a sound investment.
The England international became Louis van Gaal's second signing of the summer window following the arrival of Ander Herrera and the fullback will receive a significant wage packet in the region of €200,000 a week.
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The deal sees Shaw become the highest-paid teenager in world football but Silvestre believes that the four-year contract represents a good investment for the club.
He told Goal at an event celebrating Chevrolet's sponsorship of Manchester United's home shirt: "You have to look at the entire deal here.
"Okay, the sum is £30 million (€38) but how long has he signed for? Four years. So you have to keep that in mind as well. I know it's expensive if you look at it this way but when you join Manchester United you don't stay there for just one year, you will probably be there for four or five years.
"I stayed there for nine years. So overall, after six or seven years, you won't say that it was an expensive deal. It is a good investment by the club."
On Van Gaal's appointment, Silvestre stated his belief that the Dutchman will be a success at Old Trafford, while he is expecting the 62-year-old to make more moves in the transfer market following the acquisitions of Shaw and Herrera.
"As soon as he was announced as the new manager, I was convinced that he will be a good one for United," the former France international continued. "He has a great record for both club and country and he is just showing that in the World Cup with Netherlands. He has got what it takes to be a manager for a club like United and he is coming at the right time.
"There have already been two signings and we can expect more by the end of August, so we will see then. They lost two center backs this time and so we can expect the manager to sign a couple of experienced players in that area."