Why does "price" revert to blank when the "next" button is clicked?

I was able to see this problem in your jotform http://www.jotform.ca/form/51755082536256

the issue is being caused by erroneous condition rules that updates the Price textbox.

I suggest you re-design the form and use Calculation Value instead.

user guide: -How-to-Assign-Calculation-Value

and remove the condition rules that update the Price

You can check my test form http://www.jotformpro.com/form/51761003398959

You can clone the test form also. -How-to-Clone-an-Existing-Form-from-a-URL so that you can check in your Form Builder how I setup the form.

Let us know if you need further assistance.

Thanks.