Adding setup cost to subscription payments when using variable pricing.

How can I determine an initial "setup" fee for a subscription that is using a variable price? The option is disabled. We must collect a one-time fee per subscription but we also must have variable pricing options. 

Unfortunately it is not possible to have a setup cost for a subscription if you are using variable price. If you want to set first custom payment cost, you will have to disable the variable pricing.

The only workaround I can suggest would be to have two versions of the Auth.net payment integration in your form, so that instead of variable price for membership dues, you can set a default price for the Individual and Couple options and also have an initial setup cost. Here's a guide on how you can have two auth.net integrations on the same form: How to Create a Basic Multiple Payment form.

If you need further assistance, please let us know.
Regards.