Tons and tons of items flood the market place at high to normal value and buyers flock to purchase quick upgrades or enhancements. Sure this part of the weekend is great for sellers and demand usually takes care of undercutters very quickly, but it’s when you get deeper into the weekend and most buyers stop showing up that things get interesting. With reduced demand but many auctions that didn’t sell the day before being posted at 48 hours, the supply to demand ratio completely flip flops. Instead of high demand, medium supply you now have low to medium demand and way too much supply. Prices plummet in response. A wise auctioneer will sell like crazy with everything he has from Thursday night to Friday night and then buy the leftovers Saturday morning and on into Sunday.
If so, with which items?
Personally, I see this happen constantly with materials more than any other items. I call Saturdays "Saronite Saturday" for a reason! Other enhancement items like eternal belt buckles will drop like rocks Saturday into Sunday and then sky rocket throughout the week from pvp and pve rewards. The materials for these items tend to be proportional to their end products.