People on KSL are strange. Every gun on there has "only a few hundred round" put through it. I have sold a few on there, and buyers will ask this question. I reply, "Who knows, it does not have a round counter."
Most firearms hold their value really well, so it is not uncommon to see them priced close to that of a retail store. After sales tax and a background check, it may be a little cheaper.
I have bought a few firearms from sellers that put "Must show a CFP" in their ad. None of them ever asked. I think it is just to deter possible criminals from calling them in the first place.