This is a planned set not just a 'throw spare parts together to shovel them out the door' type set. It'd be far easier to churn out some Battlepacks or even put the Minifigure Parts in the BaM bins than to create a set around them. To me the wall-like base is no different than some of the other... packaging details LEGO has included over the years, there's a been a cave, a sarcophagus, a mask, a Zepplin/blimp to name a few. I'd expect the mold for the base is nowhere in the same league as the ones for the building pieces, and that's just fine. It doesn't HAVE to be, it's an accent piece basically. The real draw of this are the building pieces and THOSE look to be a great value.
Thumbs up LEGO, thumbs up!
Build? I merely Acquire atm.