It’s using OLEDs (Organic LEDs) for the keys which only became reasonably priced or able to be mass produced like 1 or 2 years ago (they only started showing up on digital cameras last year, and those are the first products to really use OLEDs). So yeah, it didn’t get cheap until recently.
Also a problem with OLEDs is that over time their picture quality degrades and are prone to burn-in like your CRT TVs and monitors. I’d be curious what they do to prevent burning in the letters on the keys (which in everyday usage aren’t going to change much). Don’t buy the first ones they release so that they have time to work out the kinks. 🙂