I get the feeling they felt not having actual league prizes was hurting the game significantly. (And from what I've seen, it WAS to a point.) The added expense (which probably isn't THAT much more in the scheme of things) is probably less of a problem than the lack of promos was.
Oh, and StormFront, Masquerain would make for a terrible league promo. It's a very specialized card, and league promos should really be aimed primarily at the less experienced players. (Cards that do both, especially Trainers, can work for both newer players AND older ones.) If I had to pick Pokemon (rather than Trainers/energy) to give as league promos, I would likely go for cards like Reshiram and Zekrom that are good and have some competitive worth, but still simple enough for a young kid to grasp. (Hmm, in hindsight, not sure Reshiram fits that.)