The most valuable item ever appraised at a Roadshow event (unaired) was a collection of autographs from every Presidential cabinet member from George Washington to Franklin Roosevelt, valued at a million dollars. Not surprisingly, the owner did not wish to appear on the show.
One of the show's most famous "big discoveries" was a Seymour mahogany card table, bought at a garage sale by a New Jersey retiree decades previous for $25. She later sold the table at Sotheby's through one of the men who appraised her table on the air, Leigh Keno, for over half a million dollars.
As of January 2010, the show's most expensive appraisal ever shown was an 18th Century Qianlong Jade Collection, acquired by the owner through her father who served in the military as a liaison. After learning that some of her items had imperial seals, she decided to take them into the roadshow to learn more about them. Much more to her delight, she also commented that she had several other pieces still at home that she decided against bringing in.