this faq of just dice i dont quite understand about the house edge part...
why receive 2 times your stake if there was no house edge???
What does 1% house edge mean?
Some people have been confused by this. They ask when we take the 1% off, is it after each win, or when they try to withdraw. It is neither of these. The house edge is built in to the payouts. When you play the 50% game and win, you receive 1.98 times your stake as your payout. If there was no house edge, you would receive 2 times your stake. 1.98 is 1% less than 2. That is the house edge.
You are right. Some interesting reading:
http://en.wikipedia.org/wiki/Expected_value