I have no idea what numbers comics have to bring in to stay viable or to make up for production costs and provide a profit. My guess is at least a million. But it may be alot less than that. Depends on the production cost - but based on sale price alone?

I don't know either, though I think it may be less than that. In any case, I know DH are very pleased with the Buffy comic and it's unlikely Allie and co see any reason to change what they're doing.