Jeter l'argent par les fenêtres

Literally: To throw money out of the windows

Example: “Acheter un nouveau téléphone chaque année, c'est jeter l'argent par les fenêtres.” — Buying a new phone every year is throwing money down the drain.

English equivalent: To throw money down the drain

Origin: The window matters: money thrown into the street is not merely spent but scattered where anyone might pick it up, so nothing is received in return. It is about waste rather than extravagance.