1
general::
Also, right on the money. Exact, precise, as in Your estimate is right on the money. This term alludes to a winning bet in horse racing. [Slang; 1940s]
American Heritage Idioms
2
general::
Phrase(s): on the money [and] on the nose
exactly right; in exactly the right place; in exactly the right amount (of money). • That’s a good answer, Bob. You’re right on the money. • This project is going to be finished right on the nose.
McGrawhill's American Idioms And Phrasal Verbs