Out the window = wasted, no longer exists.

“If I buy a $6.00 latte every morning from the cafe, that’s $42.00 out the window every week!” = That is $42.00 wasted every week.

Also – If an idea or plan is no longer good or possible we say it goes out the window.

“I wanted to get up early today and watch the sunrise, but I didn’t go to bed until 3:00 am so I was too tired. My plan to wake up early went out the window.”

“My plan to climb Mt. Everest is out the window!”