I agree with Kenren, at LEAST $15 because you are so amazing at what you do and no one should pay any less.
I have seen people with less awesomeness charge up to $50 for manips, and they're not nearly as good as yours, Nams. Suffice it to say, I think you could get away with the $30-60 range at-least. I don't have much experience with this (no-one ever commissions me so I don't even bother with prices XD) but from what I've seen... there you go.
Well, it needs to be at least $15, methinks. Since that's what the point value comes up to on a complex point commission or whatevs of yours. I feel like $20-$25 is the most you'll be able to charge and still get enough requests to make you happy. $30 or more is too expensive for a lot of people. But really, you should ask however much you think is right, because people will want your work regardless <3