Not sure if I buy this, the only other significant party that takes its share of profit are the theater owners, and even the theater profit split is greatly exagerrated, the studios take home usually like 70+% of box office for the first couple of weeks (which means front loaded films are actually good in a sense for studios). After that it becomes a 50-50 split. Overseas splits are even more favorable for studios.
This is why you popcorn and drink costs $10 at the theater, because concessions are where theater chains make real money, not off the actual movies.
But other than that, WB owns DC Comics so they're not splitting that with anyone.
And there's a metric asston of Batman Vs. Superman merchandise and forthcoming Blu-Ray/Digital/Cable On Demand/TV rights for Batman Vs. Superman to come, they will easily make a profit on this film.
Studios also often inflate production costs because they want profits to appear as small as possible to avoid paying out large point deals for actors/directors (ie: many big actors/directors often structure their salary to get "points" as in a percentage of the profits).
It doesn't go down to maximum 50-50 after a while. It starts in the favour for the studios but after weeks it's more like a "most goes to the cinema". That's why people always use this 50-50. It's probably more like a 60-40 in favour of the studios for frontloaded movies like BvS was but still...
That's why we have cinemas "specialized" in showing older movies, they get almost everything when they show them. The few people who go in these cinemas aren't really enough if it would be really a 50-50 split + popcorn and coke...
Then you have markets like China where only 25% go to the studio even on day 1 so a 50-50 WW sounds plausible. Maybe a 55-45 but probably not really more for the average movie. Heavily frontloaded movies maybe more, sure.