I missed the "Funding" details.... How will the textbook writers get paid? One-up contract? Write me a book for $100k (one year's worth of work) and keep it up

I missed the "Funding" details.... How will the textbook writers get paid? One-up contract? Write me a book for $100k (one year's worth of work) and keep it updated every year for $20k with typo fixes and new exercises? This would create the right incentives, since 100k is probably more than any textbook publisher will give you -- even if you make it big, and your book is used in many universities.