Unfortunately, this is in fact the law when you donate a single item or group of similar items with a value of more than $5000. You not only must have goodwill sign the form 8283, but you must also have a signed appraisal, and the appraiser must also sign form 8283.
You will have to claim a donation value of $4999 or less in order to remove the requirement to get the signature. This is why large donations must be discussed with the recipient in advance to make sure that they are willing to accept the donation and provide proper documentation as to its value.
