What is the best way to express the range from $4.5 billion to $5.2 billion?
Is the following correct?
... between $4.5 and $5.2 billion...
According to this guide on using numbers in writing, when writing numbers:
It goes on to give the following examples which are all considered correct:
Since the key is to be consistent and keep it simple, I would suggest writing your range of numbers like this:
There is an example from the Wall Street Journal that uses this style, citing:
You can also omit the first "billion" since your decimal of 4.5 probably won't be confused with $4.50. There is an example in writing here which refers to the range "between $85 and $190 million", so you can expect that people would understand the omitted "million" or "billion".
Though there are examples for both, it may be best to keep both "billions" in formal writing, so as to decrease any possible ambiguity.
According to this site, use figures only when it takes more than three words to spell out the number:
Thus, it would be written: