Each blister pack comes with a booster pack of a special set and a random promo card. They cost $5.99 each. If you buy one, you get another half off.
These are repackaged products by third party companies, like those “Mystery Boxes” you often see at Walfart. These companies usually buy leftover bulk to sell them. Pokemon never released individual booster packs for these special sets; they were always within promo products.
Thanks goes to Aaron K. for the news!