In order to split test the price on a order form you actually need to use two order forms, and move the split test to the step that comes just before the order form.
Step 1: Clone your order form
Step 2: Setup a product on each order form with two different prices (change copy as required)
Step 3: Go to the page that comes just before the order form and setup a split test on it
Step 4: Alter the control/variation so the copy on each reflects the two different price points you are testing
Step 5: (option A) If your submitting a form on this page, use the "on submit go to" field to send them to the correct order form when the form in submitted
(option B) If you are not collecting information create a direct link to the correct order form, with a button, text or image element.
Step 6: For whichever order form comes first use the "on submit go to" field to send them to the correct next page (oto or order confirmation)
Video Table of Contents:
0:25 Cloning and preparing the order forms
2:00 Setting up the split test on the page before the order form
2:55 Dealing with form submission (on the step before the order form)
3:44 Dealing with form submission (on the order forms)
4:44 Testing / Demo end result