How can I make it so that people cannot register without paying?

http://marcuslandry.com/landrys-total-body-basketball-camp-2017/

Wufoo forms allows users to register our form without paying. 

Do jotform's forms stop disable users to finish the form without paying?

Once you have finished to configure your payment form you will be able to set it up as required so your users will not be able to proceed without completing the payment. 

To set the payment field as required, simply click on it and the gear icon, turn on the required property: 

Hope this helps.