Ending? Spoiler Alert
The brother's suicide was supposed to show that everything Iris did was in vain. To avoid any ambiguity, she says, "What did you do?" or something to that effect.
However, I suspect that the rich guy had him killed, and made it look like a suicide.
There are several reasons for this:
1)It would save him a lot of time and resources/hassles. Not only would he have to spend a lot of money, but there may be legal consequences with the transplant.
2)It would eliminate a potential witness. In the event that Iris shared what happened with the brother, he may potentially tell someone, which could lead to the rich guys' arrest.
3)The millionaire said she was perfect because she had no close family who would worry. I suspect that they killed him right after she entered the contest. This is because in the likely event (7/8 chance) that Iris did not win, he would not tell anyone of her disappearance. Remember, even though she did not tell her brother about the contest, the millionaire did not know this. It is reasonable to assume that she DID tell her brother about the contest, which was arranged by her doctor, and if the brother told police of this, they could trace her disappearance back to the millionaire. I suspect that all the contestants had no one close to them who would call if they were missing. If they did, those people would probably be eliminated.
I think that the ending was meant so that the audience knew that he was murdered, but she believed the staged suicide.
What do you think?