When the word "dollars" is said and there are numbers above a million with the figure and the word, the dollar sign is used, and the combination is considered to be a unit and uses no hyphen. (NOTE: It is perfectly fine to use all figures for these, though it is probably easier to read in the figure-word combination.)
...They spent $1.2 million for the house.
...It is more than $10 million in loans.
The word "dollars" becomes singular, "dollar," when this combination is used as an adjective. It is said as "two million DOLLAR loan." The dollar sign is still used. However, because the combination is already considered to be a unit, there is no hyphen.
...They received a $3 million loan from the bank.
...It is a $1.2 million increase over what we expected.
...It is a $2 million-a-year payment for ten years.
So when a suspension hyphen is needed, it looks like this:
...It is a $10 million- to $20 million-a-year commitment.
Happy punctuating!
Margie