My immediate thought was that there is a third variable controlling both experience in rationality and willingness to pay for cryonics, such as 'living or hanging out in the bay area'.

Well, only 13% of “experienced rationalists” are signed up for cryonics, which hardly counts as “everyone else” -- unless the thing they do because everyone else is doing it is “I'll sign up for cryonics iff I think it's worth it”, which kind of dilutes the meaning.

(Anecdata: in each of my social circles before I entered university, to a very good zeroth approximation either everyone smoked or nobody did, but nowadays it's not uncommon for me to be among smokers and non-smokers at the same time. Sure, you could say that in some circles people smoke because everybody does, in some circles people don't smoke because nobody doesn't, and in some circles people smoke iff they like because everybody does that, but...)

As army1987 said, only a small percentage of experienced rationalists sign up for cryonics, so I wouldn't expect there to be social pressure. I think a more likely explanation is that experienced rationalists feel less social pressure against signing up for cryonics.