Recently I read and tweeted an interesting article cautioning photographers about the points to note in taking part in photo contests. I happen to have a well-known artist friend who has been repeatedly invited to be an adjudicator in relevant contests. From his experience, there are quite a number of organisers who he suspected have their eye more on grabbing either rights or money or both than on promoting the art. With reference to a particular real-life example, the artist revealed that an organiser could actually make a handsome profit from a payment-required contest after deducing the administrative cost and prize expenses.
Incidentally, some months ago, I stumbled upon a website of a local photo contest. Interested, I went through the terms and conditions only to find that participants were required to use the designated paid service (of an organising partner of the contest) to order a "photo book" (for putting in the participant's photographic entries) for entering into the contest. It just sounded too suspicious to me. I personally think it wise to shun any contest which asks for a fee in any form.