have you ever heard of seforim stores? Do you think the guys that own the stores learn them all? This is seforim which were collected with the mind set to be sold...
It wasn't implied at the outset that you are selling Seforim that were acquired for resale.
That being said, I knew one, and I'm sure others have heard of, or knew מוכרי ספרים that were תלמידי חכמים that actually knew the merchandise they were selling (not on the level of the Tzemach Tzedek, but at least some superficial knowledge of some, and thorough knowledge of others).
No need to get defensive, I'm not criticizing you, just suggesting some additional learning.