Kind of. I pencil on paper, but then scan it and draw over it again on computer instead of inking on paper. It's give a very clean line, but still looks natural. I do a webcomic that's done entirely through Manga Studio however, so it's pretty flexible for black and white drawing. You can ink on paper and scan it in as the import/export functions are pretty good so adding final tweaks/tones/fonts is pretty easy.
I'm not especially good at the technical side of these things, but I think it's jpeg files only (some people prefer TIF, which you can get through Photoshop and others, but I've never had a problem with it).
In terms of justifying the price you save money on not having to buy materials such as tones/paper/ink/etc. Tones especially. Letraset has them at over £1 per sheet:
http://www.letraset.com/manga/shopdispl ... Tone+MT38+
They're not reusable if you mess it up or anything, so for that alone it works out cheaper if you use the program to any extent.
You can't save your work, but there's a trial version if you wanted a play:
http://manga.smithmicro.com/d_trial_offers.html
(for fight scene inspiration - watch lots of martial arts films! XD)
There's a bunch of books ot there, but I'd assume they mainly go for American formats (although that might be what you want). Might be worth a search on Deviantart?
I've got no real idea how it works really, it's an art as opposed to a science so I fake it, lol. Big pictures for important/cool things, otherwise small. And use establishing shots to set the scene. So long as it's clear for the reader which way they're supposed to be going there's little you can do wrong imo. It's surprising just how significant the placement of dialogue is. (sorry, I didn't answer your question at all ^^; )
Long post it long! 
I'll shut up now as I'm no real authority, lol. >_>;
