That's an interesting concept - sort of what I expect from many mobile keyboards in some ways. Such as almost certainly a lousy typing feel, so you are compromising for that portability. It is a heck of a lot more compact than the typical mobile keyboard though.
I may have missed it, but I couldn't find anything about an expected price once shipping - just prices for early adopters - and apparently there are two levels.
My best guess is that the regular price will probably be $100 for the basic unit, so the same as the TB.
But I didn't see anything there about pairing to multiple devices which would, at least for me, make it a lot more expensive since I'd need more than one unless I went through the hassle of re-pairing every time.
Also, now that I've used the TB so much, I have seen how having totally individual keys make it easier to tell if you are hitting the keys correctly. After all, before getting used to the TB, almost all my errors were hitting a different letter on the same key than what I wanted. You can feel the "wells", but it isn't as obvious as a separate key.
I imagine this thing would suffer from that even more.
But if I didn't have a TB to compare to, I'd probably look seriously at this roll-up device just for when I'm desperate and limited to my iPhone or iPad.