I'm not sure I agree with many of the responders.
There is such a thing as the "blue book". just like other blue books out there, one can find the high, low and average sale prices of items.
This gives a very good idea of what items are worth and what they are typically selling for.
When I buy and sell, I try to have a good idea of what the item is "worth" or what they are selling for.
I typically list items for sale at slightly below average blue book sales price.
Because I don't like to haggle. i understand other countries and cultures.
I sell for what I feel (after research) what the item should be priced at (actually, slightly lower).
I try to not be desperate to buy or sell and I have a firm commitment to walk away or not respond if the offer is stupidly low.
Another thing, people some times feel that your listed price is one that they can dicker over. When in many cases, it is already below blue book and it is what it is.
Also, not every used item should be and is listed at 50% below new. That makes no sense to me.
If it is rare, it may be priced at higher that new or higher than blue book. If it is still in production and not old at all, then no way will it be priced at 50% of new.
my prices are slightly lower than blue book based on the condition (that I list honestly every time). So, I don't really haggle much on the price.
enjoy