22 percent to be exact.
An investor has lost money selling their 2014 Topps Allen & Ginter Baseball Silk #121 Bryce Harper card that's serial numbered 10/10 and PSA graded Gem Mint 10 (certification verification number 23985573).
That investor had originally purchased that card for $99.99 (plus shipping) on July 6, 2015, and they sold that card for $78.00 (plus shipping) on July 30, 2015. That's an approximately 22 percent drop in value.
Silk cards are inserted into 1:440 hobby packs (or approximately 1:18.3 hobby boxes).
The second best selling Silk card in that series on eBay over the past three months is Manny Machado's #75 card which sold for $33.52 (plus shipping) on June 7, 2015.