I paid $30 for the PCBs
Where are PCBs so cheap?
pcbwing.com, they are the best! That said without having tried anyone else =) They have always been very helpful and the boards seem to be top quality.
Out of curiosity, is there a reason you didn't use SPI or something like that for communication between the modules, and rolled your own?
I don't know if I would call it my own.. It's the serial protocol of the shift registers and LED driver. Very fast and simple, and I don't really know what either I2C or SPI is. I just make stuff work =) But I suppose putting a I2C-able controller in each part of the system and then connecting those together is still very viable.
ZXCVB seem to all be shifted over by one key. B is going to be a real pain in the ass to reach.
The picture would just be an example of how you could do it. With full programmability you can of course choose whatever layout you want. Myself I always used the key next to my my pinky for the 'Z'-key in contrary to how you are "supposed" to do. On my daily keyboard I have a 2 unit shift and ZXCVB like in the picture above. I never had any trouble reaching 'B'. That's actually only half a unit extra reach for 'B' and at least my index fingers are quite reachy. Or if you happen to use 'B' very often, put some other letter there. Also 'B' is not a very common letter, at least not in the English language.
There is of course also no reason to stop at tweaking the physical key placement. Why not change the layout as well, dvorak, colemak or whatever you think is best for you? Try this instead.