How to have variable cost based on drop-down menu choice

Also, I want a variable of paper cost based on a drop-down menu choice. How do I apply a specific value to each drop-down menu number?

You can assign a calculation value to the options of the Dropdown list field.

User guide: https://www.jotform.com/help/301-How-to-Assign-Calculation-Value

OR

You might as well use a payment field instead and then use Special pricing.

User guide: https://www.jotform.com/help/265-What-is-Special-Pricing

Hope this help. Let us know how it goes.

Thanks.