Custom Fields

Here’s a demo file showing how to add custom fields into the ‘Add to Cart’ interface:

https://github.com/joedolson/plugin-extensions/blob/master/my-tickets/custom-fields.php

And here’s a demo file for custom fields in the checkout process:

https://github.com/joedolson/plugin-extensions/blob/master/my-tickets/my-ticket-custom-cart-fields.php

I’m not sure what you mean by “costs for this plugin” and “transaction costs”. Can you clarify?

There’s no charge for using the plug-in; whether there’s a transaction charge would be dependent on your payment gateway, but there’s nothing built into the plug-in.