They can create 100 sketches of Chase Utley and all of them are 1/1s because they're all unique art.
Early non-sports sets used to actually number sketch cards based on how many the artist did, but since they are all (usually*) unique art, that kind of faded away.
2003 Inkworks Scooby-Doo! Mysteries and Monsters - Sketch Cards #SK-2 - Dave Crosland /284
Courtesy of COMC.com
*some artists took this way too far, like Ryan Waterhouse who basically became a laughingstock for drawing the same crappy picture of the Indiana Jones monkey or skull for a thousand sketch cards. While he can be a talented artist, his rep was trashed for mailing it in. Now Topps only paid a couple of dollars per sketch card produced, but most artist had more pride than that.
2008 Topps Indiana Jones Heritage - Sketch Cards #_RYWA - Ryan Waterhouse /1 [EX to NM]
Courtesy of COMC.com
https://www.comc.com/Cards/Non-Sport...rhouse/4494628