The cost reduction applies only to generic mana in the total cost of spells you cast from anywhere other than your hand
While we've had dominant decks and cards like Collected Company, Siege Rhino, Pack Rat, and Rally the Ancestors, those formats didn't see huge drops in attendance, and for the most part, by the time the outcry got loud, the problem card was already close to rotation (if you look at Rally and Bant Company, their most dominant times were in the two or three months before they rotated from the format)
Maybe the buyer liked the adorably tiny trophy
the recently-discontinued Pokmon Trading Card Game Online and its successor, the new and accessible Pokmon Trading Card Game Live beta
Strong international demand continues supporting premium prices
Thats something that really turned me away from other card games like Yu-Gi-Oh or Magic: The Gathering