I'd bet money (on something)
I'm so confident that I am right (or that you are wrong) that I'm willing to bet on it. Oh, with your GPA, you're definitely going to be named valedictorian—I'd bet money on it.
I'd bet money (on it).
Fig. I am certain. Charlie: Do you think Joe's planning to sell his house? Tom: I'd bet money on it. I'd bet money that Jane will get that job.