Finding a “Fair Trade Price” for a card

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At MTGPrice.com our goal is to always show how much a “fair” price is for a given card. To do this, we gather prices from all over the Internet and show them, along with their history, on our card pages.

We noticed a serious outlier today with the TCGPlayer.com “average” prices – several cards had been input incorrectly by a single store and this skewed the average price of all cards significantly. To avoid this occurring in the future, we’ve decided to implement a new version of Fair Trade Price beginning with updates tomorrow.

The new algorithm works as follows:

We aim to find prices of cards that have been sold recently. “Recently” is highly dependent on the card itself – Black Lotus typically change hands less frequently than a play-set of lightning bolts, for example. It’s important to get a value for how much a card sells for, not how much it is listed for. I can list 500 Lightning Bolt’s for $1000 each on Ebay but unless someone buys them, this price is irrelevant. Our algorithm therefore is essentially a weighted average of the current prices at various stores, weighted by the number of sales those stores typically have.

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How do we know how many cards a given store sells? We don’t, not really, but we can guess based on the inventory levels that the stores publish. We’ve been collecting inventory information from all the big stores plus Ebay, amazon and all the tcgplayer.com stores for over a month now and we feel fairly confident in our initial ranking of weights.

We normalized the weights so that Ebay count’s as a multiplier of 1. Our first attempt at weighting sales is as follows:

Ebay x1

Starcity x0.84

ABUGames x0.64

MTGMintCard x0.22

TCGPlayer LOW x1.12

As we add in other stores and update our data, these weights will change. We will update all weightings on the 1st of every month to show how important each vendor is in our index.

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How do these weights work? An example:

Liliana of the Veil is currently (11/20/2011 at noon) listed for:

Ebay - $35.62
Starcity - $39.99
ABUGames - $47.99
MtgMintCard - $52.99
TCGPlayer LOW - $32.13

The calculation that we do is as follows:

((35.62*1) +(39.99*0.84) + (47.99*0.64) + (52.99*0.22) + (32.13*1.12))/(1+0.84+0.64+0.22+1.12)

= $38.63 Fair Trade Value

This calculation will start being used on all cards starting tomorrow – we’re just running the final tests now to ensure we catch all the outliers and bad data before it comes into the calculation. Specifically, we throw away any single event that is more than 3 standard deviations away from the mean, unless there is more than 1 such occurrence. Later, we plan on using (stat’s geek alert!) Chauvenet’s criterion to detect outliers instead.

We want our prices to be the fastest and most accurate on the web. If you have any comments on how we plan to do things, or just want to say hello we can be contacted at webmaster@mtgprice.com or on Twitter or Facebook, or post in the comments section below.

 

Track your collection's value over time, see which cards moved the most, track wishlists, tradelists and more. Sign up at MTGPrice.com - it's free!

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Olivia Voldoren Spikes from $5 to $15 in a day because of Chopin’s MTG Worlds Deck!

Tweet showing Chopin's deck may cause a price spike of Olivia Voldaren

It looks like our data that was pointing to a big spike in the price of Olivia Voldoren were right – she went from being a $5 card to a $15 card in less than a day on the back of Patrick Chopin’s MTG Worlds decklist.

A guide to the deck can be found here: http://www.youtube.com/watch?v=9R8FLpMTyIc&feature=player_embedded#!

Or for those of you who prefer text, here is the full deck list:

3 Olivia Voldaren
3 Snapcaster Mage
2 Precursor Golem

1 Wurmcoil Engine

1 Inferno Titan
3 Liliana of the Veil
3 Mana Leak
2 Galvanic Blast
4 Forbidden Alchemy
3 Slagstorm
1 Devil’s Play
4 Desperate Ravings
1 Go for the Throat
1 Ratchet Bomb
2 Doom Blade

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4 Darkslick Shores
1 Copperline Gorge
4 Blackcleave Cliffs
1 Rootbound Crag
2 Drowned Catacomb
5 Mountain
3 Swamp
1 Island
1 Shimmering Grotto
4 Sulfur Falls

Sideboard:
2 Ancient Grudge
1 Geistflame
1 Slagstorm
1 Mimic Vat
2 Curse of Death’s Hold
2 Surgical Extraction
1 Wurmcoil Engine
1 Flashfreeze
1 Negate
1 Mana Leak
1 Dissipate
1 Galvanic Blast

If you’re interested in getting news of other spikes before they happen, sign up for the MTGPrice.com beta test herehttp://mtgprice.us4.list-manage1.com/subscribe?u=07d6a68d22fc116a82f58ee7b&id=2ecd5b9b12

The beta starts on December 1st and will let users learn of upcoming shifts in the trading landscape before anyone else knows about them, allowing users to act quickly to snap up the cheapest cards before they are gone then flip them for serious profit.

Trading at the MTG World Championships

Planning on doing some serious trading at mtgworlds? Read this quick guide to make sure you get what you need!

1. Figure out what you want before you start trading

Our biggest trading tip is to know what you want before you start. If you’re looking to build a standard deck, make a list of exactly which cards you need and try to stick to that list while trading. Just because someone has a foil Snapcaster Mage doesn’t mean that you should trade for it if you’re looking for 4 of something else.

2. Make sure you know what cards are worth

Once you know what you are  looking for, it’s important that you don’t get conned out of your best cards. At big events like worlds, almost everyone is friendly but a few are very aware of the fact that they won’t see the people they trade with again and act like sharks. It’s a good idea to use the MTGPrice.com MTG Card Search either on a laptop or (ideally) on a smartphone so you can see how much various stores charge for a given card.

For more complex trades, we strongly advise using the MTG Fair Trade Wizard to automatically price cards as you add and remove them from the trade.

3. Check the condition

Most prices are for “mint” cards – that’s cards that have never been played with, or only very lightly played in sleeves. If the card you are trading for isn’t mint, be sure to point this out and use it to your advantage – ask for more in return.

4. Know how to spot a fake – especially on older cards

Older cards are both valuable and easy to fake. Look carefully at any card over $20 or so in value – does it feel like a regular card? Does it bend correctly? Are the Colors looking good? Is the border correctly colored? If you’re not sure or feel uneasy, just walk away.

5. Trade up!

In general, it’s better to trade several low value cards for a single high value card. High value mythics and older rares tend to hold their values for longer periods of time (and even increase) whereas lesser cards are typically forgotten when they rotate out of the current tournament block.

6. Know what is rotating in (and out!)

Speaking of the current tournament block, pay attention to what is coming up in the next few months. Standard-powerhouse cards that were once worth a lot of money may be underpowered for Modern and so will see a significant price drop. Try to dump these cards and pick up similarly-prices cards from Innistrad instead.

We hope this short guide helps you with your trading at mtgworlds. If you make an especially great trade, or simply want to vent, feel free to post below.

tcgplayer.com support added – moving towards first beta release!

We’re steadily moving towards our target “beta 1” release date of December 1st. We still have a few more major vendors to add, some tweaks to make to the “fair trade price” algorithm (which I’ll outline soon), two major features and a LOT of bug fixes (right now, Planeshift is entirely missing and the site has lots of missing prices and some missing cards.) Oh, and foil cards too 🙂

Still, we’re making steady progress and met another milestone yesterday with integration of the prices from tcgplayer.com and their affiliated stores. TCGPlayer collects information from a large number of smaller stores – something that si generally harder to track and we greatly appreciate them allow us to use their data on this site.

As always, if you have any comments, please let us know below!

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