The crafting material cards have two purposes.
1) You can redeem the code online in the UDE points store for 100 UDE Points. These are used to purchase various items such as tokens, binders, and online objects like tabards.
2) The crafting material cards are also part of a redemption scheme. For example, you could post off 15 Primal Fires, 6 Bolts of Imbued Netherweave and 4 Nether Vortexes, and UDE would send back a Belt of Blasting card:
For further details, check out
http://entertainment.upperdeck.com/wow/en/news/article.aspx?aid=3450.
These cards have nothing to do with getting online materials.
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