The Jolteon VMAX (SWSH184) card can be found in the Swsh Black Star Promos set.
Recently sold 89 times and based on those sales is worth around £12.75.
Currently, there are 65 open listings for this card on ebay.
This card sells in the range of £8.41 to £17.09, making it stable.
This Promo card was illustrated by Hasuno.
The fact that it is a VMAX card makes it one of the more valuable cards.