Whether you use a third party app or your own website to host Facebook competitions, there are a few guidelines you need to follow to best promote them.
360 Degree Media Group Blog
The price of running a Facebook competition all depends on your approach.
In the past, companies were required to run Facebook competitions strictly through third party applications. However, Facebook recently changed its guidelines, allowing companies to either use a third party app or run the competition directly through Facebook. This can be a key piece of your facebook marketing strategy and can help measuring success.