I looked at the site. I am no master of pedagogy so take what I say with a barrel of salt, but it seems to be a lot of talk about learning Japanese, and not a lot of actual learning of Japanese. That being said I didn't look too deeply into it.
Will it help you pass N1? Possibly, if it has a listening component. Many Japanese sites are heavy on kanji and grammar and light on listening (and of course speaking is next to impossible without an actual person to speak to). JLPT doesn't test speaking, though. I think your focus should be not on passing a test, but actually being able to use the language in real life.
Anyways, $100 could get you a variety of Japanese materials. If I were you, I would compare Textfugu to other premium sites such as JapanesePod101.com and see which offers the most balanced approach that suits your learning style.