There isn't anything stopping you from making the entire screen black except for the legends, probably
$400+shipping for the display panel (a competitive price from the shop). Even at volume (which an enthusiast keyboard won't be) it's still very expensive.
The ED133UT2 is also available from E Ink directly and from other shops, but I haven't seen a significantly better price. There are also some other boards with the same controller around. An alternative to using the IT8951 is to hook the display up to an MCU with an adapter board for the flex cable directly and then drive the waveforms from the MCU, this is more complicated however and a little controller talking SPI is quite nice to have.
There's also a 10.3" with an even higher resolution that is very nice for various applications.
The cost of the panel makes me cry but there's nothing like e-ink :)
I have indoor and outdoor air quality sensors in my apartment; the outdoor air quality monitor is an LCD and the indoor one is e-ink. I kind of like the LCD better, but have to use a feature to turn off the screen at night so it's not illuminating the entire room with its backlight. The e-ink doesn't emit light, but it also doesn't update as frequently, so it's often displaying information that's out of date. Because of the various pros and cons, neither technology seems like a "win" over the other; the product designer has to pick one and hope the market agrees. LCDs get the nudge because of cost, though.
Except perhaps product designers wanting to make a flashy product that draws attention all the time, 24/7, pushing through '''features''' that leverage (force) full screen animations in the driver software.
I am bitter, yes, I met too many excellent hardware ruined by stupid, oversized, look-before-function attitude software. Making it grand and flashy (eventually overcomplicated and ugly) not because it is useful but because they can.