That's the only way I could see someone sending them a second book. Even the wackos that post on their message board and act as if that company is the second coming of Jesus would wise up once their first check arrives in the mail.
Sadly, that's not true for the hardcore faithful. When I ran my own insurance agency one of the tenets I ascribed to was "a business should meet a felt need." Most of the people on the PAMB, if quizzed, would say their need is being met.
IMHO, the current crop of the PA faithful mainly consists of the willfully ignorant, the aggressively illiterate, and the hopelessly naive. Their "felt need", that of being really-for-sure-published-authors, is met by PA, and in spades. No wonder they're tickled pink; they never had a greater desire other than sell a few copies of their work to their friends and family.