I have absolutely no idea why you'd immediately jump to that conclusion; DC could easily and justifiably offer this service for as little as $5.99 and still make a profit.
Its a big company. They're going to get their money, and they're going to get as much as they can. They're certainly not going to charge CBS All Access prices. Best cast scenario, its Netflix like prices. I can't see them offering all that for less then $10, especially since they're making a bunch of original shows, and I wouldn't be surprised to see it a lot more then $10.