375 isn't that high of a bar to reach. 

Even BvS despite all the flak it takes likely is going to net Warner Bros. a pretty large profit. 

Also the assumption that movie studios only get 50% of a movie ticket isn't even that accurate, in the US, they really take home more like 60-70% of the ticket split, that's why movie theaters have to charge so much for popcorn and drinks. 

ScarJo - $20 million for one movie.
W. Smith - $25 million for one movie.

That's really not much difference.  And her draw as a movie lead is not very big. 
http://www.boxofficemojo.com/people/chart/?view=Actor&id=willsmith.htm
http://www.boxofficemojo.com/people/chart/?view=Actor&id=scarlettjohansson.htm

I probably would've signed Will Smith for the movies and scaled back some of the CGI budget and marketing.

He would've added $50-$100+ million in the film's international gross fairly easily and increased home video sales by probably the same amount.

In the end as the studio you end up walking out with more money in your pocket. 

My understanding is that they can make 70% for the first week, but it drops off after that.  I think 50% is a better estimate.

From the following link, "...they paid about 51.8% of ticket revenue as film rental...":

http://www.rogerebert.com/letters/how-your-ticket-price-is-divided

And I agree that concessions are a big part of their income.

Like After Earth?

After Earth is not associated with Will Smith like ID4 is. Indepedence Day basically made Will Smith the biggest movie star on the planet for a while, quite frankly he was a good fit for that role too, heroic, yet funny and cool. 

It's not crazy to say ID4-2 would make more money with Will Smith than without him. It's a film people associate with him. 

So yeah sure, I'd ID4-2 might make say $500 million worldwide as is, but with Will Smith maybe that number goes up to $600 million instead, and then you have a corresponding bump in home video revenue too.

It sounds like the real bottom line here is that Will Smith simply did not want to do the sequels, he wanted to do Suicide Squad instead. Most likely the studio would've pushed out the $$$ to have him back. 

After Earth is not associated with Will Smith like ID4 is. Indepedence Day basically made Will Smith the biggest movie star on the planet for a while, quite frankly he was a good fit for that role too, heroic, yet funny and cool. 

It's not crazy to say ID4-2 would make more money with Will Smith than without him. It's a film people associate with him. 

So yeah sure, I'd ID4-2 might make say $500 million worldwide as is, but with Will Smith maybe that number goes up to $600 million instead, and then you have a corresponding bump in home video revenue too.

It sounds like the real bottom line here is that Will Smith simply did not want to do the sequels, he wanted to do Suicide Squad instead. Most likely the studio would've pushed out the $$$ to have him back. 

Wait what?  After Earth is a Will Smith 'make my kid a star and promote my alleged closeted religion.  It couldn't be more Will Smith than if Will Smith married Will Smith and give birth to a Will Smith.  It was a giant ego trip nepotistic flop. 

ID4 was a HUGE movie.  As others have said, one of the biggest.  It was the first move in a long time to challenge Star Wars.  Many other people could have played the Will Smith roll.  It did make him a star, because it did well and he got rolls after this.  But I think anyone who had that roll would be a star.  And because ID4 made so much money, they would be cast for at least the next 4-6 years.

It's like Terminator.  It made Arnold Swarzenigger a big star, but it wasn't because he is a great actor, but because James Cameron is an amazing movie maker.  Arnold fit the part because and lucked out.  Some of the movie it’s not even him, it’s a stop action puppet – and super creepy one at that (effective.)

Will Smith was greedy, and frankly, I think it will be a better movie without his ego all over it.

It's more likely that the studio would have lost money with him on board unless he got paid way less than his asking price. The movie is going to bomb anyway, with a budget of $165M. No need to bomb with a budger of $215M.

And in case you missed it, the star power effect is gone now. Franchises and brands are what brings people in.

It would've been an extra $25 million for Will Smith for this film. Which means the film would've had to make an extra $45-$50 in total box office to justify having him. 

To me I would done it as a movie studio, I mean this is not a small movie, if you're already spending $200 mill, you might as well go all in. Besides I think a lot of these marketing budgets are over-bloated. Shave $10 mill off the marketing and/or effects, you don't need 858404949848398483 layers of CGI.