I'm curious as to why the association with Watsi was the deciding factor for you. Certainly, there are causes that are equivalently significant as those being confronted by Watsi, and indeed, organizations that do similar work. The fact that you'd be willing to support a cause associated with Watsi but not with another organization is indicative that Watsi has done something correct in their branding strategy and PR efforts.
I think he was trying to say he wouldn't have bought a $40 poster without some charitable tie in. I imagine it wasn't the only worthy cause that would have swayed him. That said, Watsi is popping up a lot with the "cool kids" lately. Chelsea Clinton tweeted about them yesterday. Getting PG on the board got lots of buzz. They're trendy, and that's fine as long as it gets more people the medical care they need.
IMO his purchasing decision is legitimate. I think he liked the poster regardless of the charity element of it, that aspect just makes paying $40 palatable.
