You make a valid point. However, with regards to actors and athletes, for the most part these people initially used their talent rather then their looks to make money. Do you honestly believe that Dwyane Wade and Kobe Bryant would be making as much money as they make in endorsements if they weren't averaging 30 pts a game season after season? If Lebron James wasn't a high school phenom, do you think he would have been offered a $50 million contract from Nike? Or what about Tiger Woods and Roger Federer? Do you think anyone would pay attention to their looks if they didn't have the careers that they have? Maria Sharapova? A beautiful woman, no doubt! But if she didn't have a game to back it up, nobody would pay her any mind. I know this because there are some gorgeous women on the WTA tour who don't make as much as Maria or get as much attention because they don't a game like Maria. Lets talk about some of the top actors in Hollywood. Denzel Washington, Nicole Kidman, George Clooney, Angelina Jolie just to name a few. If George Clooney was not a brillant actor, or was just a no name, he would not have been People Mag's (or whichever magazine it was) Sexiest Man Alive. So yes they derserve to demand $20 million a flick or whatever. In all these cases, these people used thier athletic/acting ability to get to where they are.
However, with models...you're right, the system is what it is. BUT...models are just pretty faces. Yes some of them may be intelligent, I mean 158 I.Q. intelligent. Some of them may have acting abilities. However, Gisele and Ale have capitalised off their faces. And I'll admit, it has to take an incredibly beautiful and sexy woman modeling nothing but bras and panties to make another woman buy...well, bras and panties. So I congratulate you Ale!! But does she deserve $15 million a year? She's done her job, so perhaps. I personally don't think so, but like you say, it is what it is.
Just my 2 cents! Actually thats more like $4 but whatever