Truth is;
1- The place to discuss pricing is here in the Market watch forum, ...no sweat I'll move it for you 
2 - If someone will buy my used camera for $1,800, why should I not take that rather than your offer for $1,600.00?
3 - Yes, I agree with you 100% that often People do ask to much,.. I see it as often as you do.
4 - But why belly ache about it?
They either won't sell it, or they will, (in which case you and I were wrong anyway.)
The sale item was never rightfully mine, so why let it work me up?
When they don't sell, often they reduce the price, so.. ?
And again, i just don't see the point in worrying about the ones that refuse to ask a reasonable price and thus DON'T sell anything.
Personally, frankly I always feel I ask a pretty reasonable below average price when i sell, and include all shipping and extra accessories of they are appropriate to the gear I'm selling. When I decide to sell I tend to want to move it!
And yet, there are times when i get the lowball PM. Sometimes I except. Sometimes they are insulting.
I've even had buyers ask me, ME to break the forum rules for them. rofl!!!
Needless to day they are on my "never do a deal with" list.
My tip, (and hate to give away secrets) is to set a price you will pay in your head, and then wait. If you see one that comes close, make the offer via PM.
Be polite, if you insinuate that they are gouging, you will not get a deal. ( I made an offer on something today,. and it was accepted. And no, I did not think the seller was gouging actually the asking price was really close to what I would pay, so i asked)
Anyway, it's totally valid to PM an offer.
The reason Price Policing is not allowed is that often right after some pushy marketplace troll does so, the guy will sell it anyway as it is the BUYER with the ludicrous expectations.
There is no reason to allow a curmudgeon like that to ruin someones thread.
The road is two way for sure.
Rule Number One for the Bargain hunter?
Shop the bargains! Ignore the rest.