The phrase "cost/pay the earth" is often used to refer to something that is very expensive or costs a lot of money. Some synonyms for this phrase include "break the bank," "burn a hole in your pocket," "empty your wallet," "cost a fortune," "take a toll on your finances," "put a dent in your budget," "set you back a pretty penny," and "be a budget buster." These terms all emphasize the high cost or expense of something and convey the idea that it will be a significant monetary burden. When considering expenses, it's important to plan and budget accordingly to avoid any financial strain.