The use of a Forbidden/Limited list instead of an annual set rotation is one of the aspects that separates the Yu-Gi-Oh! Trading Card Game (TCG) from its competitors. Because players can use even the most obscure cards from any point of the game’s lifespan, we’re able to see sudden price spikes when a new archetype comes along.
Red Nova

Red Nova originally debuted back in 2016 in the Dragon of Legends set as a Secret Rare before being reprinted later in 2019 as a Common.
The story of this card’s market analytics is as straightforward as it looks. Doomed to wander the bargain bin pile of second-hand markets, copies of Red Nova (of both rarity types) were sitting at less than a dollar for the longest time. Then, a couple of days ago, starting, copies of Red Nova started selling for an average market value of $9 to $10.
Even now, some copies of the common variant of Red Nova are exchanging for about $15; the secret rare, some copies are already pushing past $25.
Given the fact that Red Nova had only seen two print runs, the movement in the second-hand market may be highly dependent on a couple of factors. The first is how well Red Nova will perform with the archetype that’s causing this change. The second is how many copies of Red Nova are actually available.
If the first parameter holds true, then Red Nova’s value will steadily climb upwards, doubly so if it turns out that this tuner monster ends up being an integral piece of a combo. As for the second parameter, scarcity has always been a force multiplier when it comes to second-hand market value.
Red Nova’s last printing was roughly five years ago. If the demand for Red Nova ends up outpacing all available supply, then the market might just see copies of Red Nova skip to higher values without pause.
We’re already seeing this happen with the Secret Rare copies of Red Nova. There are a couple of odd copies here and there already being sold at upwards of $30 or $40.
Cause of the sudden value rush
Red Nova’s sudden popularity and value spike come from the new Killer Tune archetype that is debuting in the Phantom Revenge expansion this December.

More specifically, we can attribute Red Nova’s meteoric rise to the newly revealed Killer Tune main deck monster, Killer Tune Cue. Differing from the other search cards of the archetype, Killer Tune Cue is able to special summon any Tuner monster from the graveyard, hand, or the deck.
Using Killer Tune Cue, assuming the play line is undisturbed by negation handtraps, you can instantly grab your copy of Red Nova. From there, Red Nova comes in as not only fodder for any of the Killer Tune synchro monsters, but as another extension to grab Killer Tune Reco.
Killer Tune Reco just happens to fall under the purview of Red Nova’s special summon targeting parameters as a Fire Fiend-type monster. The most criminal thing about Red Nova’s special summon is that it doesn’t negate the effects of its target. This extends the combo further as you use Killer Tune Reco to grab Killer Tune Clip.

It cannot be understated how much Red Nova synergizes with Killer Tune. Not only that, but Red Nova answers one of the more difficult problems Killer Tune has in its overall package: easy access to the Level 4 synchro monster, Killer Tune Track Maker. This synchro monster is also another searcher for any Killer Tune card upon special summon.
With one interaction between Killer Tune Cue and Red Nova, you can essentially bring out one Synchro monster, which searches for any named Killer Tune card, and two other Killer Tune main deck monsters. Suffice it to say, that's a lot of mileage.
Assuming you’re just using in-house pieces, you’d have to find a path to accessing both Killer Tune Mix and Killer Tune Clip, as they’re the only two Level 4 monsters in this archetype. There’s just a lot more hoops to jump through without Red Nova in the deck.
The Killer Tune archetype can technically function without Red Nova, but there’s a lot less consistency and a lot fewer resources the controlling player can have access to off a single card.
For those interested in the Killer Tune archetype, Red Nova looks to be an auto-include in the deck list. At the very least, one copy should be used to help facilitate easy access to not only Track Maker but just getting your other Killer Tune monsters into rotation as soon as possible.