But what is the cost of posting on X? Why do they even have a blue tick?

It lends legitimacy to a declining site controlled by a white supremacist and filled with more neo-nazi’s by the day.

The fewer legitimate organizations posting on twitter, drawing eyes and views to the site, the better.

Its a bit silly to say that they are declining. For its specific niche (mass short form/viral content) there simply aren't any relevant competitors that even come close.

More than the cost of not posting on X.

That cost should be $0, so that's not the issue.