Why is the cheaper model much more comfortable AND solid?

It kinda irks me that the 720 NC are such a perfect design and so incredibly comfortable and light, but I'm buying replacement pads for my XM6.

I'm not going to go Sony headphones again unless they go back to a headphone design like XM4 or 720 instead of making space suit accessories.

As much as I love the Sony sound, they have got things quite backwards with the design.

I want to see XM7 build nearly identical to XM4 , or I'm done and moving on to other manufacturers.