Directv can't negotiate for AT&T at this time. At best, they could add something to the contract that states that the same price includes up to x million additional subscribers as a result of merger/acquisition, but that would leave them overpaying if that deal was shot down by the government.
As the price goes up, some bars will drop NFLST. Some of the smaller places around here already have over the past few years as the price keeps going up by 10% a year. If they bump the contract another 30-40% as it sounds like they're doing, most of that increase will be passed to the commercial side, since half of residential customers who get it do so as a freebie, and they'd probably lose more than a few if they tried to bump the price from $299 to $399. I'm not close to dropping it, but if the price went up by another 50% I'd have to take a hard look at whether it is really worth having.
Who said they are negotiating for AT&T? A potential merger is a complication.
If structured like previous contracts, DirecTV is paying a flat fee to the NFL and then marketing the product and reaping whatever they get in sales. Profit and loss is there issue. What I am saying is that DirecTV is probably factoring in (from their judging of the value) the potential customers from a merger that looks like it will go through during the contract period. It is still a risk. They may overpay a bit if the merger falls through but they are probably not balking at the price if they can extend it to any merged company.
As for your pricing analysis, I will go with the DirecTV guys on their projections over yours. I think their economic modeling has held up well over the years. Hell, they dropped the price for non-commercial accounts recently. I am sure they plugged that into their model and decided it made sense. And here they are coming back for more, so that is pretty good evidence that they are not in any kind of financial trouble with Sunday Ticket.
Of course, there are those who will say DirecTV needs ST or they lose too many customers, despite the actual numbers that show a minority of DirecTV households sub to ST. They are interested in the business customers, though. They are important to ST. And I think they know that.
Me, I don't care what they pay for it. I just care what I pay for it. When prices are set per sub, that has a more immediate impact on my pricing. When it is a flat fee, it does not as it is dependent on how successful they are in pricing it.