I think the issue here is going to be overhead. I'll provide competing examples:
Nike has been pulling its shoes from many retailers and selling DTC via their website. On a $100 pair of shoes, they probably wholesale them for $40. If they sell DTC, the extra $60 is right in their pocket as almost pure profit instead of someone like Foot Locker. Overhead to maintain website/customer service/fulfillment is minimal because they already have to have this infra set up. Going pure DTC is a win-win for them. This is also why they can afford to do free returns all day long.
I don't know what the per sub costs are (maybe someone does and we can run some real numbers), but say ESPN, Fox, and WB are $20, $5, and $5 respectively. That means they have to charge $30 to make back what they would have gotten from the viewer as a cable sub. Never mind the ever increasing cost of content. HOWEVER, they now have the added overhead cost of running this service - website, servers, stream bandwidth, developers, support, the list goes on. It's not like they can "reassign" all the costs from people that were working on delivery to cable/sat to these new jobs because they still have to maintain cable delivery. So what additional overhead is needed to make money here?
Unless this thing sells like gangbusters and economies of scale kick in, they are gonna have to put a minimum $10-15 on top of the $30 in order cover overhead and make a small profit.