I did the same experiment on a Raspberry Pi 2. The net saving was 5.803 seconds, so 5.803 microseconds per call.
Obviously if you care about performance then you wouldn't be running your program on a Raspberry Pi in the first place. But for everything else there's this free speed up.
I build a bunch of home automation stuff (as a hobby) using Pis and other microcontrollers. Performance in those things translates almost directly to power savings, and is very desirable.
OTOH, I've never encountered an issue like this on those systems.. (yet)
Obviously if you care about performance then you wouldn't be running your program on a Raspberry Pi in the first place. But for everything else there's this free speed up.