So this curse and the mark is focused on the act itself. What is the value of the blade? [Alucard's tone suggests that that clarification is actually useful.] And as for the act itself - is it weighted because of the act of murder generally or the specific act of killing one's sibling? That information might--

[The word deal though. That's different. Enough to stop Alucard in his train of thought, and to reach back for the paper. He flips it over, making a few hurried notes about the ground already covered.]

To answer specifically, I'd have to know the particulars of a deal. Mostly the terms. What is said is where a chance for renegotiation lies. Unless you especially want me to dig into theology here.