It looks like the announcement of the new D/D support has stirred the second-hand market a bit. Some of the old archetype support cards have suddenly spiked in value despite their relative obscurity.
D/D Swirl Slime - (Quarter Century Secret Rare [QCSR])
Originally released in the Dimension of Chaos expansion back in 2015, D/D Swirl Slime has gone through many reprints over the years. Most recently, D/D Swirl Slime has gotten a print in Quarter Century Stampede
Around the tail of April, the QCSR of D/D Swirl Slime could easily be found trading hands at about a $4 average. This slowly increased through the early days of May until the 10th, when it reached a $7 average.
Then, over the course of a weekend, copies of the QCSR more than doubled their average selling price to about $20.
Since then, the card has slid back down to a market average of $16, and it seems to be holding steady. That said, there are some singular sales reaching over $20.
D/D Swirl Slime used to be a prominent part of the D/D engine back in its heyday. It basically functioned as the in-archetype fusion spell. At the same time, D/D Swirl Slime would help preserve the normal summon with its graveyard effect.
According to online communities like Yu-Gi-Oh! Meta data collected has shown that modern versions of the D/D engine can easily get away with a single copy of D/D Swirl Slime.
If spending for the QCSR doesn’t interest you, there are still common copies of D/D Swirl Slime in second-hand markets like TCGplayer that are exchanging hands for $2 or less.
D/D/D Abyss King Gilgamesh
The other D/D support that climbed out of obscurity over the announcement of Doom of Dimensions.
Released back in 2020 in the Duel Overload set as an Ultra Rare (UR), D/D/D Abyss King Gilgamesh was sitting at less than a dollar since April. But on the day of the original announcement for the new D/D support, more than 800 copies were sold on TCGplayer.
The card has climbed to about a $3-4 average during the weekend before sliding back down to a $2-3 range. There are some outlier sales where copies of this card were sold for about $8, though.
While the market value doesn't rival that of the D/D Swirl Slime QCSR, it doesn’t change the fact that this extra deck monster has not seen a single reprint at the moment.
D/D/D Abyss King Gilgamesh can be considered as one of the main play lines for the archetype. It allows D/D to bring out a full set of Pendulum Scales from the deck for just 1000 life points.
Given the recent announcement of D/D support, this ability is all the more important due to the reveal of D/D/D Zero Demise King Zero Machinex having a scale of 0, allowing a D/D deck to pendulum summon its important Level 1 combo starters.
Should D/D/D Abyss King Gilgamesh get destroyed by an opponent’s card, then it can float to another D/D monster from the extra deck.
D/D/D Abyss King Gilgamesh’s effect is good enough that players are actually running two copies of it in their Extra Deck despite its 'once per turn' clause.
There is a chance that as the new D/D support cards get closer to reaching the western market, D/D/D Abyss King Gilgamesh might just have another spike in value.
With no reprint announced, there exists the possibility that the demand might end up outpacing the supply.
Konami Announces New D/D Support with Doom of Dimensions Expansion