Thats how I think of it. While the practice of making certain cards exceptions to the rules has probably been around for as long as people have played cardsthink jokers wildGarfield pushed the practice to unprecedented proportions
Flubs loads the yard for cards like Underworld Breach and Mizzix's Mastery with ease
Cowardice Cowardice is normally a fairly weak card, but in Nadu specifically, it's fantastic
Now, TCGs low on foils
Essentially, if you have a full party with all four of these on the board, you can pay one white, one blue, and one black mana to give the Warrior lifelink, deathtouch, and make him unblockable (deathtouch and unblockable at the same time has no real use, but thats still OP to think about)
Another very high contender for the most expensive cards in Unlimited is Chaos Orb