Hey,
There is a built-in payment form that might suit your needs, you can find more info about it here .
If you have more questions about it, you can contact Wix Support and they’ll be able to help you.
https://support.wix.com/en/article/contacting-wix-support
If you want to create a custom registration form with payment, you can use the Wix Pay API to do it.
E.g. have a conditional statement which enters data into the database only if the payment is successful.