While I'm no political pundit, I am a self-appointed arithmetic pundit. Mitt Romney:
You put $90 billion into green jobs. And I — look, I’m all in favor of green energy. $90 billion, that would have hired two million teachers. $90 billion.
I guess it could have hired 2 million teachers for one year at $45k/per and no benefits.
And then you have had to fire all of them, b/c the $90 billion would be fully spent.
If you were funding new teachers that you intended to keep on the job, however, the cost isn't $45,000 for one year. It's $1 million to $4 million apiece, depending on the discount rate, annual salary increases and pensions, and whether you want to model a whole career (say 30 years) or forever (like an endowed professorship).
I guess the sentence "You could have hired 2 million teachers with $90 billion" worked better in Romney's pre-debate focus groups than the more precise "You could have hired 30,000 teachers..."