If the card is a first edition, look at the circular first edition stamp to the lower left of the card's picture
For a sealed booster box, the value looks pretty reasonable on a per-pack basis
But there wasnt a clear incentive to the shadow mechanic back then
It won't be long until the World Eaters get their Warhammer 40k codex release date, and we'll have a guide ready when they do: until then, if you want to get a sense for how the firm has approached 40k chaos factions before, check out our guides to Chaos Space Marines, Death Guard, and Thousand Sons.
The correct answer will be according to every collector's needs and interests
This build allows you to take full advantage of all the support Psychic-types get while having Mewtwo ex there to compensate for Mew exs shortcomings