So you can be informed without the need to start a new thread, this will remain stickied. Please read and try to use tips in this thread before posting a new price request. Also feel free to add to this thread if you have a suggestion.
First and foremost: If you're seeking prices for loose NTSC games, consult our latest free price guide in the NintendoAge e-Zine (on the website homepage).-------
eBay: the world's price guide
There are many bad ways to harvest price data from eBay, and two good ways. Some people simply type in the name of their game in the search box on the frontpage and look at the various prices that pop up. "What's that, my Legend of Zelda is only worth $0.99?" Of course not, it may just be a new auction without any bids.
So what are the two good ways? To look at what an item is immediately purchasable for, and what an item has historically sold for. Here are three links from which you can start an easy search. I use variations of these links on a day-to-day basis. Note that you must be logged in for the last one. Take a moment to click on them before I explore the details. The will be for loose Kid Icarus carts for simplicity.
http://search.ebay.com/kid-icarus-nes_W0QQcatrefZC6QQdfspZ1Q...
http://search.stores.ebay.com/kid...http://search-completed.ebay.com/...The first two links will bring you to a list of BIN's for both eBay stores, and eBay auctions. They are sorted by price+shipping, lowest first. Take both into account, add them together and you have the lowest price you could buy this item for right now, shipped to your doorstep. Useful if you're either listing for sale, trying to find relative trade values, or selling to a board member. A good global price.
The last link is historical data of what this item has sold for in the last two weeks. Also a useful gauge of value, this is real data on what people have paid for an item. This would seem more accurate than the first group of links, but keep in mind that many things can affect a cart's value. Bonuses like a manual or case, a seller with exceptionally high feedback, or a bid war can affect the selling price and so these prices should be taken into consideration, but not always used as a rule. You'll note these are sorted by highest-first. So this link shows the most an item has sold for in the past couple weeks.
If you're looking for something specific, like the price for a manual or box or CIB or such, try adding these to your search. Cut and paste them right into your search box, after you've clicked the links above:
(book,booklet,manual,instructions)
(cib,complete,boxed,box)
(new,sealed)
Adding these to your links above, you can see how much a CIB Kid Icarus sold for last week, and is currently available at BIN for, and use that to find the "fair market value" of a similar item.
For some items, like Super Mario Bros 3, you may get lots of "false hits" on items that aren't the game you're looking for. Plush toys, shirts, stickers, and even other games (in this case, SMB/Duck Hunt/WCTM 3-in-1). You can filter your results by resubmitting the search, with negative keywords:
-(duck,plush,shirt,sticker,decal) --useful for most Mario items
-(book,booklet,manual,instructions,cib,complete,boxed,box) --if you just want to see loose carts
One final note: be sure to click into an auction before you quote it as a price. Look for indicators that may affect value, like use of a stock photo, condition of the item in listings that do use a real photo, and presence of items bundled with it - i.e. - "lots" of items.
Using these links, and perhaps modifying them to fit your own needs, you should have no problem finding a good price WITHOUT the need to ask all 600 users on the board in the form of a global post in the price check thread.