As I mentioned in the new comics thread. I don't think it's so much 'not working' as they don't need it to as much. DC had hit the doldrums before Rebirth. They needed a hit desperately and for the new direction to work and took a profits hit, now they don't need to as much.
It's all a balance of supply and demand. Conversely while Marvel's Legacy isn't as cheap they are in need of a big hit right now and they have been selling comics of a similar size in the last few months for $9.99 so have come down 40% to give this a boost.
We'll see if they have calculated correctly when the sales come in. If either are deeply disappointing I expect the loss leaders could return.