How typical was Tammet/Corney's commercialization, in the context of other memory sport competitors?

After reading this page I've been wondering how common it is or has been in the past for claims to be made about neurodevelopmental conditions and disabilities and memory sport champions. I've also been wondering how common it is for such champions to use their status to promote businesses that offer self-improvement courses, talks or books or packages or all of these. 

http://www.happychild.org.uk/acc/tpr/features/0205domo.htm