Price fields are the most basic field in Paperform for accepting payment. They allow you to set a fixed price, or to include a payment where the amount is entered by the respondent (often used for donation forms).
The price field can be used in two modes:
The price is fixed, and can't be changed by the submitter of the form. The price is set in the question configuration (as pictured above).
Often used for donations or sliding-scale pricing, this allows the submitter to type in a custom amount. You can optionally set a "Default Price," and/or use the "Minimum Price" setting to prevent submission if the answer is below a certain amount.
When a Price field is hidden with visibility logic (either on the question itself or on the page/section that the question is in), its price is removed from the form's total. This means you can actually use Price fields to dynamically change the total by showing or hiding them with logic.
If you'd like to charge a certain amount without displaying it in a Price field, use Custom Pricing Rules instead.