From 4,000 yen *6 (including parts)

On the day

The various buttons on the iPhone are the volume buttons (volume up and volume down buttons)
Some of the buttons include a silent switch (switch to switch to silent mode) and a sleep button (button to turn off the power).

The sleep button is one of the most commonly used buttons on a daily basis, so it is the second most common part to break after the home button.
This is true for other buttons as well, but it is rare for the buttons themselves to break.
If the parts that secure the buttons on the back become loose or misaligned over time, the buttons may become sluggish or stop working altogether.

*Various buttons are faulty, but replacing the parts may not improve the symptoms.