She's definitely got some werewolf in her if she's already got a taste for blood.

....ok, that's not fair to other werewolves, including her mother.

Now I suddenly have the idea that they pay diabetics for their blood when they are hyperglycemic so they get sweet bloodcicles.

Why B-type blood is so special? (Remilia's favorite is also B-type)

I posit that, logically, it would be the rarest, hence most expensive type, specifically talking about B-.

Blood contains either A antigens, B antigens, both, and has either a Rh+ or Rh- factor.

If you look up blood types per population, for Japan, the rarest is AB-. But, you could conceivably mix up types A and B, assuming the antigens is what the vampires can taste, to create an AB substitute (which would make a little sense; it's what determines transfusion compatibility), to make "AB-", so it costs then less than half the price of B-.

Then again, who knows? We value more things irrationally.