Way too exspensive. I'd stretch to $99. He should be offering discounts for stundents too.
This looks like an excellent use of $399, and worth the investment. Now to convince someone that this is a legitimate business expense..
I'm intrigued that you say that. This is essentially a typography ebook, albeit a very pretty one, for 10-20x the price you would usually pay. For comparison, Matthew Butterick and Danny Truong offer similar resources using a donation only model (with suggested amounts of around $20).