Howdy Justin,
This is something we are interested in doing. Please voice your support here.
The specifics are not nailed down yet. One of the issues we run into is how to implement this. Traditionally we offer integration with various third party shopping carts, from WooCommerce to Easy Digital Downloads. In order to allow people to pay to submit an event we will either have to tie into an existing service like we have in the past, or roll or our own. Both options present their own complications, as well as pros and cons.
This is a fun question. You can already accomplish what you want with hooks and filters. For your specific needs it sounds like you could hook into ‘tribe_community_is_field_valid’. Check if the field is the cost field, if it is greater than x amount of $, and the current user has no meta info indicating they are a paying customer, return an invalid data flag and issue a redirect your payment page. Store their event info in the session. Upon successful payment you could add some relevant user meta using the WP API. Then you could manually resubmit the data for them via the TribeCommunityEvents_SubmissionHandler.
That last paragraph will sound less like greek once you are down in the trenches writing code, assuming that is your forte. Let me know if you have any follow up questions. I am happy to assist. Cheers!
– Brook