The single-player challenges are designed purely to help players understand how the games elemental system works - which is similar to that of the Pokmon video game series - and give them a chance to use various cards found in the wider game, which is great for helping to develop your sense of play and on-the-spot thinking
Another Charizard GX came with Reshiram & Charizard GX, which the Hyper Rare sold over $300 too at release
Unfortunately, even when sales are being held legitimately, the intense demand created by scalpers and resellers has led to concerns for the safety of both customers and employees
With enough investment, you can bypass the vanishing downside if you pair it with proliferate cards or counter doublers
Stoneforge Mystic : 1/2 creature that lets you tutor for equipment when it comes into play, and activated ability to play equipment from hand
However, these are much rarer, to the point of only being introduced as promotional cards