I've also been curious for a while why Dictum sells the 16k for less than the 10k and about their claim regarding the 16k being a 'mixed grit' stone:

- 8k = 90.70 euros
- 10k = 149 euros
- 16k = 113 euros

I purchased my 16k from them at the low price at least five years ago. I also have the 10k and my 16k achieves a better polish than the 10k, which you'd expect. The Dictum prices increase progressively as the grits increase for the 11 GS stones they sell from 220 to 30k - but the 16k is the only exception to their price progression. Strange but I'm not complaining because a) for me the performance is there and b) I love bargains!