Yet, in spite of these priors, the group you consider yourself member of is somehow the true best group ever?

You made up this 'true best group ever' idea yourself. "Best at a highly specific activity that is the primary focus of this group" is an entirely different claim.

I'm tempted to point to Eliezer outright making things up on costs of cryonics multiple times, and ignoring corrections from me and others, in case halo effect prevents you from seeing that he's not really extraordinarily less wrong.

Eliezer doesn't have all that much of a halo. People disagree with him and criticise him incessantly. Sometimes deserved, sometimes not. Most times I have seen Eliezer accused of having a halo effect have been when Eliezer disagrees with them on a particular subject and it happens to be the case that the majority of others here do too. Acknowledging that those who disagree with you may be doing so independently based on their own intellectual backgrounds is not nearly so psychologically rewarding as dismissing them as blind followers.