What is the cost as 1 Sub User?

I'm sorry, I'm not sure if I understood your concern correctly. Are you looking on to adding additional sub account users? You can increase your number of allowed sub users when you upgrade to a higher subscription plan. You can check our pricing page to see how many sub users each plan is allowed.

To see how sub account users work, you can check this guide: http://www.jotform.com/help/232-How-to-Share-Forms-with-a-Sub-Account-User 

Please let us know if you are referring to a different concern.