As a seller, I always remove the price. I value the privacy both to myself and the buyer.
I wrote earlier about "market price." Past sales in this forum should not be used as a price index, IMHO. When we have so many independent buyers and sellers with all kinds of ideas as to what their stuff is worth, I just don't think of that as being reliable at all. When I sell a knife I don't go searching the forum for past prices, I just list the knife at what I know is a fair price and see if it sells. If it doesn't, I mark it down or take it off the list. If we start a rule that makes us leave the price, it implies to me that we are supposed to use the forum as a kind of fair-price index.
Also, consider this: The listed price is not always the price an item sells for. I have taken many counter-offers that are below my listed price. If we take this into account, then it would mean that under a "leave the price rule," we would also have to re-edit the price it was actually sold for.
What if we do a partial trade with money? How do we account for a sold price then? Do we have to list what was traded and how much money was involved? (this applies only to gold members or higher, obviously)
What if I am feeling good and list an item at an unreasonably good deal? How does that help anyone set a future price? It lessens the value of the knife to the buyer, and lessens the possible sale price of anyone else looking to sell a similar item in the future.
It just isn't needed, IMHO.
Thanks for reading,
Max