How can I create special pricing with custom labels for each price?

It's not possible in Jotform's payment field. What you need is a custom payment setup.

Here's what you need to do.

1). Set the payment field as a "User defined amount" as you will be passing the total calculated amount into that field.

2). Create an individual field with labels for each special pricing

3). Assign a calculation value to each option https://www.jotform.com/help/301-How-to-Assign-Calculation-Value 

4). Pass that value to a form calculation widget https://widgets.jotform.com/widget/calculation

5). Pass the total value in the form calculation widget into your payment field by assigning the field to get the value from the form calculation widget https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field.

Check my sample form here https://form.jotform.com/91158416422959.

Feel free to clone it https://www.jotform.com/help/42-How-to-Clone-an-Existing-Form-from-a-URL so you can see how I applied the suggested method above.

Let us know if you have any questions or if you need further assistance.