The fairest trade possible would be an even exchange, like $5 worth of cards for $5 worth of cards, even if that means one player trades a single $5 card for two cards that cost $2.50 each
Card Errata Before [Your turn] [Once per turn] When you would play a level 4 or higher Digimon card with [Bagra Army] in its traits, by placing up to 3 purple Digimon cards from under your Tamers in the digivolution cards of the Digimon card played, reduce the memory cost of that Digimon by 2 for each card placed
Entei #30 Pokemon Obsidian Flames Keep track of your collection value over time
While the Booster Bundle deal I mentioned eariler is not quite as good a value as picking up the Booster Box at TCGplayer right now, including 36 packs for $228.80 market price (working out at $6.35 per pack), it's still a great deal for anyone who hasn't got a spare $200 to throw around, but still wants to get involved with the new set
PS Platinum Secret Rare QCSE Quarter Century Secret Rare Slifer the Sky Dragon X DIVINE Level 10 [ Divine-BeastEffect ] ATK