Why is there a star beside some giveaway titles for games?

The game is still worth contribution value of what it is in steam store. However, there is a cutoff point of $30.00. Contributing nothing but bundle games, means you will never get above $30.00 contribution. After that, it works by only allowing a set percentage of your contribution, to be bundle keys, before no further bundle keys add to that contribution value...There is a better explanation than this somewhere, But that's the basic gist of it.