Historically, Pokmon cards have managed to retain their value through the years, but that may not always be the case
Giratina VSTARs price is largely thanks to its dominance in the Pokemon Trading Card Game right now
The first rule is to ensure that the game can properly be played with both opponents having enough cards, however, note that 60 is just the minimum
Although I made this about 1.5 year ago, so it might contain some mistakes (EDIT: I actually already see a few mistakes)
You could pay less mana and play Seasons Past and probably still get a boatload of card advantage, but Seasons Past wont necessarily be able to target all of the things you want at the same time and it will never cost less than six mana
Giant Rock hits for 140 damage, and if your opponent has a Stage Two Pokemon, it smashes for 280 insteadtalk about punishing overachievers