I am on the fence with this one as...
a newer collector, I still dont know much about what I have, especially if it came part of a collection purchased without individual values. I have gone by the books at times and found that in this economy, I was asking to much for an item. Or if the item was from an area outside the books I have, I had no clue on value. For the most part, if I asked for offers instead of listing a price it was because I felt stupid asking too much or too little for something. On the other hand, I have been apprehensive to make offers on something if I didn't know the value in fear of insulting the seller. For me, it's more about knowledge and experience than anything else.