The former Manchester United defender said they haven't bought the defender just for one season, but for several.
Some eyebrows will have been raised at making Shaw the most expensive teenager in world football by paying approximately £30 million to Southampton for the 18-year-old, but Silvestre thinks that because he is bought for the long-term then as time goes by he will be worth the fee.
Silvestre told Goal.com: "Okay, the sum is £30m 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."
Shaw certainly has plenty of development left in him, even though he has commanded such a large figure that some would pay for the finished article. Given that he is already an England international and has several years left ahead of him there is still a lot of pressure for Shaw to be able to perform at a top level even if he is still developing.
However, given Louis van Gaal's reputation for developing and nurturing young players, few could argue that he isn't in good hands, and will probably demonstrate why United decided to invest so heavily in him.
Midfielder Ander Herrera has also secured a move to Old Trafford from Athletic Bilbao for a similar fee and Silvestre anticipates more signings this summer ahead of van Gaal's first campaign in the United hotseat.
"There have already been two signings and we can expect more by the end of August, so we will see then. They lost two centre-backs this time and so we can expect the manager to sign a couple of experienced players in that area."