Prismatic Evolutions is one of the most expensive Pokémon sets in recent memory, whether you're looking at the value of sealed products like Elite Trainer Boxes, or the Market Prices of the cards inside those boxes.
While Prismatic Evolutions contains all-star reprints from the past year of Pokémon releases, many of which have new artwork, the biggest draws of the set are Eevee and its eight evolutions (aka Eeveelutions). Every member of the Eevee family tree has its own stunning Special Illustration Rare card in Prismatic Evolutions, most of which are brand new to the TCG, and all of which have spectacular new art. Each of these nine Pokémon also has a lower-rarity card with a special Master Ball foil version, that's nearly as hard to pull as the Special Illustration Rares.
That's a lot of Eevee(lution)s to collect, and it makes all of them more valuable by association. Every one of them is going to be the last piece somebody needs to complete their perfect Eevee collection!
With that context in mind, these are the most expensive and valuable Pokémon cards in Prismatic Evolutions.
The Most Valuable Pokémon Cards in Prismatic Evolutions
#10 Eevee ex 167/131
#9 Jolteon ex 153/131
#8 Umbreon 059/131 (Master Ball)
#7 Vaporeon ex 149/131
#6 Glaceon ex 150/131
#5 Leafeon ex 144/131
#4 Flareon ex 146/131
#3 Espeon ex 155/131
#2 Sylveon ex 156/131
#1 Umbreon ex 161/131
Following in the pawprints of "Moonbreon" from Evolving Skies, Special Illustration Rare Umbreon ex 161 (aka "Sunbreon") is the most expensive Pokémon card in Prismatic Evolutions. It's not particularly close, either. At time of writing, Sunbreon has achieved a Market Price a full order of magnitude above its closest competitor, and even rivals Moonbreon for how much it costs on the secondary market.