When goldfishing, it can typically threaten a turn 5 - 6 win (turn 4 wins are also not uncommon), which puts it as pretty fast for casual but keep in mind that interaction will slow this down (if the speed is a concern, see the Powering Down section below)
NM copies usually sell in a range between $25 to $35, so it's worth getting the one in the best condition for a few extra dollars.
Most of these are identified by one of the features above, but a few cards are unusual, and sometimes valuable, for other reasons: Full art cards have a picture that extends beyond the entirety of the card, w/ text printed and overlayed atop it
First with a bonus 100 ATK and DEF for each dragonmaid card in your graveyard (spells and traps included), by the mid to late game this card will give quite the substantial boost
It could have only been Exploud
Dialga's status as a cover Legendary from Generation 4, one of the most beloved generations in the franchise, provides a nostalgia floor that keeps demand elevated among the massive Sinnoh fan community