Auction items can be added to your event at no risk. You pay for only the items that sell. The amount you pay depends on the type of item and size of the winning bid.
Raffle items are available at a flat fee that depends on the type of item. Big-ticket items (e.g., a vacation) can be purchased for 50% of the retail value. Small ticket items can be purchased for 15% of the retail value. This will be the amount you pay prior to the raffle (you can checkout from the Home tab).