I mentioned it before but I think it's worth repeating.
Sharon Lee and Steve Miller did something similar with their novels
Fledgling and now
Saltation. However, there are some key differences with King's approach:
1) You are free to donate (not "pay") once, twice, or not at all.
2) Every chapter is posted once a week (with some exceptions)
if the authors have $300 in contributions for it.
3) Every reader that donates $25 or more will get a paperback of the novel in case it gets published.
It seems to have worked wonderfully (e.g. they posted six chapters of Saltation but have donations enough for up to 15th).