Capitalism at it's best.
~OR~
Well there's the additional financial burdens like paying for voice acting, in which the casting can play a big role in it either being a success or failure, for anime fanatics this should be general knowledge.
No matter how good your story is, unpopular VA lineup will definitely ruin the initial sales. Imagine, Hirano Aya casting as a secondary lead, we all know what will happen then. It's just a worst case scenario but it can happen.
Licensing issues, royalties need to be paid to agents and recording companies. We've all seen what Mangagamer had to deal with, even if they are just localizing it.
And with content at this size, the media of choice needs to be at least doubled, again increasing the costs.
All this hassle, when all you want to do is publish your graphic story.