They set two pricing options in the event for the customer to choose like:
$350 Payment by check
$360 payment by CC
Ok, so that’s 2 different ticket options within the event and EE has no way to know which payment method should be used for either, it just knows which payment methods are available for the event itself (not the tickets within that event).
There’s no way to change the ticket selection based on the payment method selected but what you can do tell EE to only show a check payment method if the ticket name contains the string ‘check’, you can do that using this example:
Add that to a custom functions plugin on your site and if the user selects a ticket that is named ‘Payment by check’ EE will only show a check payment method, otherwise it will show all payment methods.