The place where it breaks down is if you want to build a keyboard that doesn't use a typical collection of contours and widths of keys or a subset thereof. I haven't found a shop that'll do a "nonstandard" collection of keys as a package and the prices for one-off custom keycaps are not economical for a set of 50 or 70 or whathaveyou.

I'm surprised the legends have 4 colours for that price, too.

This makes it much more tempting to get a set which describes something like Miryoku.