Does moving a static collider without rigidbody still cost?

Just wondering if anyone knows off the top of their head. The High-performance physics in Unity 5 blog post mentioned that moving static colliders will be a lot less expensive in U5 as they’d “use the same data structure to handle the movement of both dynamic and static colliders”.

I’m wondering if that means that adding a kinematic rigidbody is no longer necessary (and possibly just additional overhead if you didn’t need the rigidbody for other reasons), or if you should still have it and performance simply won’t plummet quite as much if you don’t.

Any insights would be much appreciated!

And as far as I understand, it’s only relevant to the 3d physics, not the 2d, right?