These contain a combination of existing cards (with brand new artwork), new cards from the main Final Fantasy set, and a further 25 new cards in each deck that cant be obtained in normal Play Boosters (though they do appear in Collector Boosters)
Seeing as this is one of the best Mega Evolutions, its only fitting that the card is so valuable
Magic requires so many different skills, and different Spikes will focus on different ones
For example, other Pokmon that ended up being Evolution cards were Basic cards during this initial design (or, technically, neither since none of that info is provided)
After that he, makes it harder to be attacked and eventually, basically refunds you the cost that you paid for it
It can still be done, but youll spend more time polishing than designing