Good solution for custom calculator

I was looking for plugin to help me build a rather simple custom rental price calculator as an enhancement for a contact form. I was positively surprised with the configuration editor, which is elegant a very useful. It even let me write the calculation logic in Javascript without any issues. I would recommend you add a section to your documentation, that using intermediate named variables is no issue for this plugin, I was looking for it and didn’t find this well documented. Then I paid for the basic license (75 $ incl. taxes) to be able to deliver the results as e-mails, I would appreciate if basic e-mail options were also included free, but I understand why it is not the case. Overall it is not expensive, provides good service and I am fully satisfied, thank you and keep up the good work!