However the regular licensing says that if you create something with it and
charge for it you have to pay $3600 for an extended license. Is that right?
I can’t fathom anyone using the robust features of the theme to create a
membership area that is free.
the main difference is that under the Regular License, your end product (incorporating the item you’ve licensed) is distributed for free, whereas under the Extended License your end product may be sold. Extended License is still limited to a single end product.
If the end users need to pay to see the end product, you need an Extended License.
Example: A website that requires money before you can access the content