In my opinion just let the author decide how many SS they will charge for each chapter of his novel
You know only the author know the best about his novel worth
Qidian can just take 10% of the author earning
I mean i doubt people will paid 4 spirit stones for my shitty quality novel each chapter
If i can reduce it into 1 spirit stones, it's still doable because i think people still willing to spend at least 1 spirit stone to read that shit if the plot are interesting enough