For reference, I don't think there is any problem with person A asking, "How much should I pay for this part?" and person B giving a suggested price/value.  Its when person A says, "How much should this part cost?" and person B responds with "I'll sell you one for $xx"; or when person A says, "I'm getting rid of this part, what is it worth?" and person B responding with "I'll give you $xx for it".  

Hopefully everyone can see the differences in the two - the first example is members helping members, something we want to support and promote; the second & third examples are clearly selling outside the EE and while most/all may think, "I don't need arfcom to protect me from scammers", others have demanded that we take steps to do so and in general the site owners feel a responsibility to help prevent fraud on the site to the extent possible.

Do the benefits of this outweigh the negatives?  This thread (and forum) say that sometimes that answer is "no".  That being said, we have to have a set of rules that apply site wide and that always creates situations where someone is unhappy. I'm currently asking other staff to help me with the value of some firearms I'd like to sell (mostly from my inlaws after passing), but don't feel comfortable asking for help in the forums because of this exact issue.

I'm an EE mod. We (EE mods) can only see reports from EE threads. We are blind to reports of any type that originate outside of the EE. Mods and especially staff have tools we use to try to keep the scammers at bay, but their methods evolve and short of nuking them from orbit, they will still get some people. Check the Comments and Questions and Negative Feedback sections of the EE for threads on the scammers and their methods.