No, a collection is just a group of games that you have set up by a certain criteria - for instance many people use a collection effectively as a "Wish List" to keep track of games they can't get now but want to in the future. Being in a collection has no impact on the price of a game, it's just for you to keep group games by genres, games you plan to buy, games you have worked on,
Collections can either be private, so only you can see them, or public so that anyone could see them.
I hope this is of some help!