I will posit another couple reasons for Spahn's second tier status among collectors.
1. People seem to get caught up in the young phenom who enters the league and sets it on fire before he can barely drink. Mantle, Williams, DiMaggio, Feller...more recently Gooden, Griffey 2, Harper, Trout. But here is Warren Spahn with 277 wins after turning 30. Here is an article that puts the total in perspective.
http://www.3-dbaseball.net/2009/06/a...faxes.html?m=1
2. Collectors and fans seem to favor strikeout pitchers with blazing fastballs...Feller again, Koufax, Ryan. Despite leading the NL in Ks four times, Spahn's high was 191 and avg was 124.