Can I use dynamic payment amounts

Yes, you may set up your options using fields such as drop downs, check boxes, radio buttons or even text box where you can capture amounts. Then you may perform the calculations and pass this amount to the payment field. 

In order to get more information about calculations, please check this guide: https://www.jotform.com/help/259-How-to-Perform-Form-Calculation-Using-a-Widget 

Also, this guide will help you passing the final calculation to the payment field: https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field 

If you have questions, let us know.