Market prices
When you look at buying a modern tabletop game, you will have a rough idea as to how much you think it is worth - or you will have some sort of budget in your head that you want to stick to, and which guides you to the sort of games that you think you can afford. Your price expectations will be based on things such as the quantity and quality of the components, replayability and probably also rarity or hotness of a game. Yet, the amount of money you're willing to put on the counter doesn't always match the real cost or value of a game and is either too much or too little in comparison.