When a figure is using normal movement through a large or massive hostile figure, does it pay an extra point for each space it must move through that is occupied by the hostile figure? Or just one extra point for the entire figure?

Page 8 learn to play book - "A figure can move into a space occupied by a friendly or neutral figure at no additional cost. A figure can move into a space occupied by a hostile figure, but must spend one additional movement point to do so. A figure cannot end its movement in a space containing another figure". A large figure is occupying all the spaces on the board it stands on, you cannot stop in that space therefore you need pay the movement costs for moving through the spaces it occupies. Well, that's how I read the rules it also, I think, makes logical sense as large figures can be used strategically to block travel for rebels and others.

I agree, it does seem like your interpretation is correct and that is how our group is playing it, but it could use better wording like maybe, "for each space occupied by a hostile figure".

I'll agree with that. You have to pay for each space occupied by a large hostile figure that you are moving through.