Speaking personally, I wouldn't spend that much. No matter how big the pen is, kittens want out of it.
We use the standard MDC kitten pens, which are really useful when getting to know them for that first couple of days, or when you want to keep them secure while cleaning out the foster room. I find that once they are confident of themselves and their surroundings, they will howl the house down to be let out. And once they are out, they won't go back in. Have you ever tried herding kittens into somewhere they don't want to go??
