I would say this is how we know. Dish knows where their subs are. (ok, except for moving
) Dish made the business decision not to carry YES, then MSG, and now SNY. They know how many current subs this would affect, and how many subs in the affected area is the norm who are new subscribers each year. Probably also take into account turn over in that area. They may also have an idea of approximately what % care about the RSN's.
Now they look at the cost of carrying those RSN's, how it affects all subs, and their profit. I would say their actions tell us that it was cost effective to not carry those RSN's. At the same time, they are probably also saying they just will not, in their opinion, overpay.