Maybe it is slightly

, but...
I am not very familiar with King's experiment but, judging from what I read from this post, one factor that might have contributed to the failure of King's experiment is that the payment is made separately every time a new chapter comes out.
People find it more painful to pay $1 each 10 times than paying 10$ at once. For example, according to Thaler (1985), one reason why credit card is successful is that it lumps small losses into one big loss. By asking people to pay a chapter separately, it might have caused more disutility to readers than by making them pay the total sum at once.
[Reference]
Richard Thaler (1985) "Mental Accounting and Consumer Choice"
Marketing Science, Vol. 4, No. 3. (Summer, 1985), pp. 199-214.