A good rule to follow is that if you have to ask how much to pay for a game or what they "go for", you shouldn't waste your money on it, as it's not valuable and familiar enough to you to know as much in the first place.
You're better off playing an expensive game on a flashcard or cdr regularly for a year, while monitoring and measuring the legitimacy of sold listings. Then you'll know both what the game is worth to you in dollars and what it has been selling for in the places you've been able to find it. If you can't get it for what it's worth to you, then save your money for something which is.
