The reason is that EX cards have a special ruling: When they're knocked out, your opponent takes two prize cards rather than one
(12/8/2022) If you discard a card with madness to pay the cost of a spell or activated ability, that card's madness triggered ability (and the spell that card becomes, if you choose to cast it) will resolve before the spell or ability the discard paid for
So let's get to some answers
Make deals in your favour, gain life, and draw cards until you find the cards you need to stick them in the back with the goat-knife
Jace is now sitting around $4 since it's been a victim of power creep, but I'm not sure these Final Fantasy Surge Foils will follow the same trend
Unfortunately, that plan gets shredded in the early game by the formats efficient removal