There are a ton of different discount options - large customers typically get between 50-60% discount based on committed spending, and AWS is pretty flexible around how that commit lands (they will allow roll overs even if they say they won't). Reserved instances get you ~70% discounts - similar to the committed spending. And my favorite - if it works for you - spot instances on EC2 come at as high as 90% off.

Nobody at commercial volume pays list to AWS - everyone gets a discount.