Okay, ladies and gents, I see lots of people around here being very, very uninformed as to how they're playing the exchange game. I feel like it's my duty to clear it up for you.
To put it simply: The codes are not worth equal "value" due to scarcity of supply (due to the place the pre-order weapons are gained from being more expensive than another place) and demand (how cool / useful the item is).
Roughly, the codes go like so in terms of rarity:-
Champion's Hammer (bought from Amazon.com and .co.uk) < Inquisitor's Sword (bought from Gamestop) < Absolver (bought from Game) < Channeler's Sword (bought from Australian shop or something and a BestBuy)
In terms of price, the Champion's Hammers are on the lowest rung, with Absolvers coming a close second (despite their rarity, no one seems to want them or their tattoos
). The Inquisitor Swords are only marginally better off than the Champion's Hammers. Standing above ALL of them are the Channeler's Swords / Tats, those things are expensive.
At the moment, prices are relatively high. The market will get flooded with sellers (and buyers, to be fair, but not as many) when the game gets released in the various countries. This will crash the price down to a very minimal one.
Over time, as the scarcity of the codes gets higher (within about three to six months) the codes are going to start running out and demand will greatly outstrip supply. I estimate the prices will return to just above current values (to about $15-$20 for Inquisitors within three months time limit, probably about $100 for Channeler Swords) depending on whether or not Fable 3 is worth long-time playing.
Now, mind that this is just speculation. IF the game isn't very long-lived, it's highly unlikely you'll get any money out of it post-collapse since no one will be playing it and therefore not want them. It's a matter of whether or not you want to hedge your bets.
Try to keep all this in mind whilst offering trades for your items. Some of your items (The Channeler Swords, notably) are worth far more than the rest especially in relative value. Don't trade them for a much more common item, try to get at least two or three before you get one.
On that note, I'm willing to buy any non-Channeler Swords. ;D
Hope this was helpful, guys.
TL;DR: NO ONE WANTS YOUR DAMN HAMMER FOR THEIR CHANNELER SWORD. OKAY?! (Some may, but they're so rare you're stupid for trying.)
EDIT: Oh, Shardborne Swords have the lowest cost on this list, since the supply (the publisher printing more books) far outstrips any possible demand (since those people can just buy a book, instead).
EDIT2: If the Australian Channeler codes are able to be used in the US, you can grab them for cheap (EXTREMELY cheap, since they're the only pre-order bonus weapons in Aus) from there. This might effect the prices slightly, but not enough to considerably change the philosophy.