It cost me 0.125 as well for a total of 0.356 drk to denominate a measly 17.999 DRK. Kind of expensive don't you think. And if denom is supposed to be .001 then why is it .0125 for some users? Another bug? Here's a screenshot. And no it's not photoshopped.
It is definitely charging .0125 per denomination round or .1 DRK for 8 rounds. Your math above seems off, but I agree that .0125 per round is too expensive, especially when anonymizing smaller amounts.