Typically when a relatively new set goes on clearance like this, it's for one of two reasons. Either a) It's not on the planner for the next season or b) it's a mistake. Stores have a limited amount of space, and they may not carry everything at each store (Walmart does this based on store size).
But occasionally, something slips through the system. Which is how I picked up 79007 The Black Gate on clearance today for $41.98.
If the above post didn't offend you, you're probably reading it wrong.