According to a Sponichi report, the Arizona Diamondbacks are preparing a total 6.56B yen ($80M) to put towards Yu Darvish (that would cover both the posting fee and his salary).
An unnamed MLB source is quoted as saying that the Diamondbacks have done all the research on Darvish and should be able to prepare enough money to be serious contenders. Diamondbacks' interim GM Jerry Dipoto was in Japan earlier this year to watch Darvish pitch and it seems both Mike Brown and Rick Short (scouts for the Dbacks) are extremely high on Darvish.
I'm not quite sure where Sponichi is getting the 6.5B yen figure from, but the article does mention that the Diamondbacks have about 4B yen coming off the books this season.
Sponichi mentions that the Diamondbacks also have their eye on Hisashi Iwakuma as well.
Incidentally, another Sponichi article mentions 5-6 teams being interesting in Darvish: in addition to the Diamondbacks, the Yanks, Mets, Mariners, Rangers, and Braves are named.