And I disagree with you.
The Spider-Man and POTC sequels had those kind of budgets mainly because stars and actors asked for a lot more money after the success of the first one. BB and TDK too are so expensive mainly for the ridiculous cachet all the actors are getting for their roles.
Morgan Freeman himself admitted he was never paid as much as for the Batman movies.
And for SR they have already digital libraries of the city and of Superman that can be reused for the VFX.
And are you sure they're not planning back to back movies to cut expenses and do them before the 2013 like they did for Matrix?
So, I think a Superman movie can be done for less than 150 million $.
And again i'll have to disagree with you
It is true that salaries take up a good deal op the budget for sequels , but i doubt that it is a massive increase , so much so that the bdget rises way above the 200 million mark.
If that were the case we'd see budgets of 200 million of the Harry Potter movies. But so far the budget has never gone higher then 180 million despite many of the actors getting paid with each movie AND an ever growing list of british actors.
Morgan Freeman can say that he has never been paid as much as when he's playing in BB and TDK , but then again as Morgan Freeman really been a commercial actors. Most of his movies are indie flicks with occasional big movies like DreamCatcher , Deep Impact etc
However there are other factors , aside from the salaries , that still can make the budget of these movies go skyhigh.
Shooting things real. On real sets , real locations. TDk cost 185 million. Yet if you look at the action it's mostly real. CGI is used to a minimum , like crowd animation and city extensions with the occasional CG batman appearing.
That's because Batman himself isn't a guy who constantly flies over his city or the world and doing stuff like saving a city from natural disasters.
Nolan shoots most of his stuff in camera.
Now compare the first shots of SPiderman saving Gwen Stacy in Spider-man3.
Let's see it's guy swinging thru a city , a crane messing up a skyscraper with a girl falling down and spiderman going thru concrete debri and capturing her.
Well good luck shooting that with live action.
Or how about the fight in SPider-man 2 with Spidey and Doc Ock.
Digital libraries are used in creating VFX but nothing is ever the same. Shots are constantly updated . I remember reading in Spider-man 3 Cinefex issue where they still had to create quite alot of CG buildings for the movie. Those buildings were put ino the foreground , the spiderman 2 buildings were combined in the fore-and-back ground shots and the spiderman 1 buildings were placed all the way back.
Digital library yes , but hardly the same.
ANd i haven't even started with the digital doubles.
Digital doubles are very tricky. Mess up one little thing and the audience can almost instantly be turned away. One of the great things about movies like POTC is that many people didn't realise Davey Jones was a CG character. He looked real. That is something that alot of CGI artists are striving for. PHOTOREALISM.
The more human your CG character is , the more difficult it becomes to create a CG character. It still costs a huge amount of money to get those shots right.
Oh and also you mentioned back-to-back shooting.
I doub the studio would go for back to back shooting if they're still struggling with relaunching Superman. The disadvantage of shooting things back to back is to get everything right the first time. Fail there and you've basically doomed future sequels.