There are maybe two or three people in the entire world who spend only the bare possible minimum on themselves, and contribute everything else to a rationally effective charity. They have an excuse for not signing up. No one else does.

I guess I agree that only the specified people can be said to have made consistently rational decisions when it comes to allocating money between benefiting themselves and benefiting others (at least of those who know something about the issues). I don't think this implies that all but these people should sign up for cryonics. General point: [Your actions cannot be described as motivated by coherent utility function unless you do A] does not imply [you ought to do A].

Simple example: Tom cares about the welfare of others as much as his own, but biases lead him to consistently act as if he cared about his welfare 1,000 times as much as the welfare of others. Tom could overcome these biases, but he has not in the past. In a moment when he is unaffected by these biases, Tom sacrifices his life to save the lives of 900 other people.

[All that said, I take your point that it may be rational for you to advocate signing up for cryonics, since cryonics money and charity money may not be substitutes.]