fall through the floor
To decrease significantly, as of a price. Whew, I'm glad I sold those stocks before they fell through the floor. Housing prices in the area have fallen through the floor as crime has risen sharply. Ideally, you would sell your company before the price falls through the floor, but you waited too long, Jim.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.