It's like the only thing worth stacking on. Single stabs aren't on sale, and I just don't feel like buying 2700 db coins on a game I prolly won't be playing in a couple months.
It's been there for quite some time now. It is almost a permanent addition to the PSN store at this point.
As far as I can see, episodes are no 1/2 price. Didn't appear to be at least on my Premium/F2P accounts. The Gear up bundle was 5$ however, which I think is 1/2 price. Also on Steam, for PC players, the ultimate edition is 40% off, but honestly if the episodes are going to remain open, it's not a great value with really just the gear up bundle + shield and the older powerset bundle being the other items in it.
The announcement says most markeplace items 50% off, and has asterisk (*). Lower in the announcement it has “ *Excludes Stabilizers/Time Capsules, Artifact XP Packs, Booster Bundle, and Holly Leaves.”. Since episodes weren’t in the exclude list, they should be on sale. But sadly, recent experience shows you can’t put trust in what’s written here.
It actually comes and goes. I've had a couple of instances where I went to purchase it and it wasn't available.