JMadiganA few things: 1. Sailor only sells these colors via the Bungubox store, so there is no real competition in sales (unless you want to substitute a similar ink, but that can be hard for some of those shades, since some of the better alternatives are from more harsh inks you wouldn't want to put in some pens), 2. Sailor inks are rising in price pretty fast over the last few years do to increased demand, so the special inks (like Bungubox, Kobe, etc.) are rising in price too, otherwise normal sailor inks would be more per ml, 3. ink collecting seems to really be taking off along with the sustained fountain pen revival, so demand for limited inks is growing really fast.