There is no limit (to ambition, aspirations, expense, or the like). For example, Order anything you like on the menu—the sky's the limit tonight, or He's so brilliant he can do anything—the sky's the limit. This metaphoric idiom was first recorded in 1920.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.