Your confusion arises because Mem Fox's honorarium was paid by a nonprofit organization. Such payments are allowed for B-1 visitors only if they are paid by nonprofit organizations, government organizations, or institutions of higher education, which I presume the organizers of your "business" conferences are not. This is specified at 8 USC 1182(q):
(q) Academic honoraria
Any alien admitted under section 1101(a)(15)(B) of this title may accept an honorarium payment and associated incidental expenses for a usual academic activity or activities (lasting not longer than 9 days at any single institution), as defined by the Attorney General in consultation with the Secretary of Education, if such payment is offered by an institution or organization described in subsection (p)(1) and is made for services conducted for the benefit of that institution or entity and if the alien has not accepted such payment or expenses from more than 5 institutions or organizations in the previous 6-month period.
(p)(1) has to do with computing wage levels so it doesn't make sense to quote it in full here, but the organizations and institutions it describes are
(A) an institution of higher education (as defined in section 1001(a) of title 20), or a related or affiliated nonprofit entity; or
(B) a nonprofit research organization or a Governmental research organization,