Can conditional logic affect Braintree, Stripe or PayPal?

We work with squarefeet. The more user space they use the more they pay.

We are looking online for help with conditional logic, where if they input they need X amount of space they pay Y amount.

PayPal, Stripe and Braintree work. But we want the price to be able to be updated automatically.

So say User comes in. Inputs he needs 500 square feet the price updates as well.

You can perform calculations in your form: https://www.jotform.com/help/259-How-to-Perform-Form-Calculation-Using-a-Widget 

If you need to perform the calculations based on conditions, here is how: https://www.jotform.com/help/268-Conditional-Logic-Inserts-Text-Calculation-Into-A-Field 

Finally, you can pass the total to your payment field: https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field