So, in the past I have "donated" boobie pictures to boobiethon, a online fundraising event for breast cancer research. This year I entered into a drawing for a free custom WordPress theme. And I won it!
You might think that I'm lucky, but actually when I enter lotteries I'm very calculating. Once when I was 10, there was a Beanie Baby lottery at the local library. You could see the jars with the tickets in them for each Beanie Baby. There was one Beanie Baby that had very few tickets in the jar, so I bought exactly one ticket for it. And I won the Beanie Baby.
I saw that for this contest, there were 5 WordPress prizes to be awarded total. For other contests there were only one. And I correctly surmised that others would try to win the more desirable prizes. I also submitted 5 pictures of my boobies, and you got one ticket per boobie picture with a maximum of 5 pictures. That's 5 entries. Donating $10 only got you one ticket. And it cost me nothing :).
It's human nature to go for the lottery item of the thing you actually want. I don't do that. I enter the lotteries for things I think no one else wants and that have multiple awards and that have a low-to-no cost. You're never going to win the monetary prize, because the odds are against you. You CAN win things if the odds are in your favor.