On one hand, it's surprising. On the other hand, let's not forget that Bob is trying to sell a book -- a book that his publisher advanced him a pretty penny to do in hopes of recouping said pretty penny upon publication.
Where else but on TPIR (in the publisher's eyes) could they target their core audience? Yeah, people will see him on "Ellen" or "Bonnie Hunt" and such, but will that result in big sales? Maybe. But not like a plug on TPIR would.
Also, let's be honest, Bob has always shown a knack for promoting himself. He knows when he appears on Larry King to discuss lawsuits that he'd better not permit calls or e-mails from viewers challenging his recollections. He knows which daytime talk shows will throw him soft balls, too. And he knows he's still exalted by TPIR viewers. So a quick, possibly pre-taped Price cameo is a $lam dunk.