Like most Pokmon cards, the value of Eelektross depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Lost Origin)
Perhaps the most important is..what the card means to the person it belongs to
Its dynamic and lively, with a color palette that plays off of the character design perfectly
If Bruse Tarl leaves the battlefield after other Oxen you control have dealt first-strike damage but before regular combat damage, those Oxen won't deal regular combat damage (unless they still have double strike for some other reason)
If at least one target is still legal, it will resolve and do as much as it can
The color palette leans heavily into stark contrasts, with bright whites clashing against deep shadows