It is difficult to determine the value of an object once it has been owned by a celebrity. However, that memorabilia can be of real value, according to Bloomberg in "How Do You Put a Price on Audrey Hepburn's Personal Treasures?"
In a few months, many of Audrey Hepburn's personal belongings will go up for auction at Christie's. That means the auction house must estimate how much each individual item is worth to a willing buyer. Doing that is more difficult than putting a market price on the item itself.
Appraisers must instead estimate how much of a premium someone may be willing to pay, because of who owned the items. That is not an easy task.
The premium people will pay is different depending on the items and often depends on how closely associated the celebrity was to the item and how much it meant personally to the celebrity.
This makes things difficult for celebrity estate administrators, who must determine what personal items are worth for estate tax purposes.
It is quite common to have the situation of not being able to determine value, until the item is actually auctioned off.