Humble Bundle provides Steam keys when you purchase their bundles. You can sell Steam keys on G2A. Why not sell the big ticket $15 items and the popular mid tier items and keep the little things? You'd earn a little profit by selling the big ticket games, maybe quite a bit of profit if the games in the bundle are popular. You also get games either way! You could have a cycle of buying and selling Humble Bundle keys and then rake in profit from it too! I know the games aren't guaranteed to sell, but with a bit of judgement you could sell only games you could guarantee would sell!