You have to wonder what it says about a group that they aren't afraid that their potential converts would find it weird that they need to pay for people to say how awesome they are.
Well, Hubbard flat out said that he should invent a religion in order to get rich long before he wrote Dianetics, so that tells you something about the typical scientology candidate's capacity for deductive reasoning.
The Church denies that though. Actually, the story surrounding that quote is a little murky but I'm sure it's true. I believe James Randi claims to have heard it. Anyway, followers of Scientology have a lot of other crazy stuff about Hubbard to make them weary of it, yet they persist.
Compared to their forced labor camps and harrassment campaigns of their critics, I'd say there are definite better things to focus on than apocryphal (but certainly possible) stories that persuade no one. It may be published in several unauthorized biographies and "vouched for" by a bunch of people who may or may not have even been at the convention, but it might as well be a story overhead in a bar for all it's going to persuade the credulous, who want to believe them with every fiber of their beings.
Edit: fixed typo