I could see $20 million a month, but billion doesn't work here since the Romney campaign didn't spend even one billion[0].

Is this one of those weird "billion means something different in my country" things? Because even then, the miscommunication is usually between billion (10^9 in most English) and trillion (10^12), in short scale[1].

[0]: https://www.fec.gov/data/candidate/P80003353/?tab=summary

[1]: https://en.wikipedia.org/wiki/Long_and_short_scales