It's worth every penny, even if you can finish it quickly. You don't pirate a movie when it clocks in at an hour and a half, do you? Or a DVD with very few extras. I've never heard anyone say "I'm not going to buy that movie because I'm going to be done with it in two hours."
Compare the price. Batman = $50. If you get more than four hours of entertainment out of it, you just beat three 1.5 hour no extras DVD movies at $15. Not bad at all.
If you really want to play it but can't justify the price, wait six months and it'll drop.