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Anytime you have a holiday when most players are off to enjoy Guild Wars 2, you will have a large increase in sales volume. If you have any kind of stockpile, especially high end crafting materials, you should be able to unload the majority of them during this time. When a lot of bots were banned not too long ago, the price of things like saffron thread shot through the roof. This weekend is when you'll want to sell, sell, sell!
Everything from armor to weapons to sigils to runes to earrings to amulets, to tridents, to food! EVERYTHING will sell well and go up in value this weekend. Same goes for any major holiday with a three day weekend.
My guess is that Saturday will be the big hitter. Gems should also go up, but probably not enough to buy today and sell by the end of the weekend (due to the excessive gem selling fees).
Let me know how your Black Friday goes selling on the Trading Post, and I'll be back to giving out my 30 Markets in 30 Days posts tomorrow.