That’s odd.
So you have no tickets selling for that cost (that perhaps are currently invisible on the frontend due to start/end sale date restrictions)?
If not, I wonder if the event cost field has, for some reason, been set to $1 and is stuck there despite the presence of the tickets. To explore this idea, can I ask you to add the following snippet to your theme’s functions.php file or some other suitable place:
add_filter( 'tribe_events_admin_show_cost_field', '__return_true' );
Now edit the event and look for the actual event cost field – what is it set to? If it is $1 can you delete the cost, update the event then remove the above snippet – does that get us any closer to a fix?