The Paid Entry Fee Addon (Extension) allows you to charge an entry fee for entering your contest. The entry fee can be set at the category level so that you can charge a different fee for each contest when running multiple contests.
The contestant will fill out the entry form and then be directed to the selected payment gateway to complete the payment. Once payment is made, the gateway will send the user back to your website and their entry will be live.
Alternatively, if you set an activation limit, lets say 20, then once the activation limit is reached, each contestant will be emailed a payment link to finalize their payment. If the activation limit is not reached, no monetary transactions will take place to reduce the chance of refunds. This function is very similar to crowd funding where if a goal is not met, no transactions take place. If the goal is met (number of contestants reached), then the contestants are notified to complete their transaction.
This demonstration also uses the Coupon Extension for WP Voting Contest Entry Fee Extension.